Photosensitive resin composition, organic EL element barrier rib, and organic EL element

ABSTRACT

There is provided a highly sensitive colorant-containing photosensitive resin composition for use in the formation of organic EL element barrier ribs. In one embodiment, the photosensitive resin composition for an organic EL element barrier rib comprises: (A) a binder resin; (B) at least one low molecular weight organic compound having a molar volume of 130 cm 3 /mol or less and being selected from the group consisting of aromatic carboxylic acids and compounds each having a plurality of phenolic hydroxyl groups; (C) a radiation sensitive compound; and (D) a colorant selected from the group consisting of black dyes and black pigments.

FIELD

The present disclosure relates to a photosensitive resin composition for an organic EL element barrier rib, and an organic EL element barrier rib and an organic EL element that use the same. More specifically, the present disclosure relates to a photosensitive resin composition for an organic EL element barrier rib comprising a black colorant, and an organic EL element barrier rib and an organic EL element that use the same.

BACKGROUND

In display devices, such as organic EL displays (OLED), barrier ribs are used in the gaps in the coloring pattern in the display region or the edge of the periphery of the display region in order to improve display properties. When manufacturing organic EL display devices, to ensure that the pixels comprising organic material do not touch each other, barrier ribs are first formed then the pixels comprising the organic material are formed between the barrier ribs. Such barrier ribs are generally formed by photolithography using a photosensitive resin composition and are electrical insulators. More specifically, a photosensitive resin composition is applied onto a substrate using a coating device, and after volatile components are removed by heating, etc., is exposed to light via a mask. Next, unexposed parts, in the case of a negative tone, and exposed parts, in the case of a positive tone, are removed with a developer, such as an aqueous alkaline solution thereby developing the same. The obtained pattern is heat treated and barrier ribs (insulating film) are formed. Next, films of organic material that emit one of three colors, i.e., red, green or blue, are formed between the barrier ribs using an inkjet method, etc., and the pixels of the organic EL display device are formed.

Recently in this field, there is a demand for more compact display devices, and due to the diversification of the content displayed, there is a demand for higher pixel performance and higher resolution. In order to increase the contrast of a display device for the purpose of improving visibility, colorants have been used in order to attempt to impart light shielding properties to the barrier ribs. However, in cases where light shielding properties are imparted to the barrier ribs, there is a tendency for the sensitivity of the photosensitive resin composition to decrease and as a result, there is a risk that the time required for light exposure increases and productivity decreases. Thus, there is a demand for highly sensitive photosensitive resin compositions to be used for forming barrier ribs that contain a colorant.

Patent Literature 1 (Japanese Unexamined Patent Publication (Kokai) No. 2001-281440) describes a composition in which titanium black is added to a positive tone radiation sensitive resin composition comprising an alkali-soluble resin and a quinone diazide compound as a radiation sensitive resin composition exhibiting high light shielding properties by heat treatment after exposure to light.

Patent Literature 2 (Japanese Unexamined Patent Publication (Kokai) No. 2002-116536) describes a method for blackening barrier ribs using carbon black in a radiation sensitive resin composition comprising [A] an alkali-soluble resin, [B] a 1,2-quinone diazide compound, and [C] a colorant.

Patent Literature 3 (Japanese Unexamined Patent Publication (Kokai) No. 2010-237310) describes a composition in which a heat sensitive dye is added to a positive tone radiation sensitive resin composition comprising an alkali-soluble resin and a quinone diazide compound as a radiation sensitive resin composition exhibiting light shielding properties by heat treatment after exposure to light.

CITATION LIST Patent Literature

[PTL 1] Japanese Unexamined Patent Publication (Kokai) No. 2001-281440

[PTL 2] Japanese Unexamined Patent Publication (Kokai) No. 2002-116536

[PTL 3] Japanese Unexamined Patent Publication (Kokai) No. 2010-237310

SUMMARY Technical Problem

In order to sufficiently increase the light shielding properties of a cured film of a photosensitive resin composition used for forming a colored barrier rib, a substantial amount of colorant is required. When such a substantial amount of colorant is used, as radiation onto the coating of the photosensitive resin composition is absorbed by the colorant, the effective strength of the radiation in the coating is diminished, the photosensitive resin composition is not sufficiently exposed to light and as a result, pattern formability is reduced.

When forming barrier ribs for organic EL elements, it is important for the material that forms the barrier rib to be highly sensitive from the standpoint of productivity. However, when a black photosensitive resin composition containing a colorant is used, insufficient light exposure occurs under normally used light exposure conditions and it is necessary, for example, to extend light exposure time which is a factor in reducing productivity.

In general, ultra-high-pressure mercury lamps that emit g-rays (wavelength 436 nm), b-rays (wavelength 405 nm) and i-rays (wavelength 365 nm) are used on organic EL element barrier ribs wherein the g-, h-, and i-rays are used for light exposure. However, as there are restrictions on the facilities and equipment of manufacturers, there is a demand for the use of only i-rays. As the total amount of energy irradiated is smaller when only i-rays are used for exposure, there is a risk that the reaction rate of a radiation sensitive compound, for example, a photoacid generator, is reduced and, in the development step, there is a risk that insoluble binder resin residue will be generated and a reduction in pattern formability will occur. Thus, it is desirable to further increase the sensitivity of a colorant-containing photosensitive resin composition and increase the flexibility in the use of the radiation for light exposure.

The present invention was conceived of based on the aforementioned circumstances and the object thereof is to provide a highly sensitive colorant-containing photosensitive resin composition for use in the formation of organic EL element barrier ribs.

Solution to Problem

The present inventors discovered that by adding a specific low molecular weight organic compound to a colorant-containing photosensitive resin composition, the sensitivity of the photosensitive resin composition can be increased. More specifically, it was discovered that by promoting the dissolution of a binder resin during development, even when a low energy light exposure, such as exposure only to i-rays, is used, a photosensitive resin composition with excellent alkali developability and pattern formability can be provided.

Specifically, the present disclosure includes the following aspects.

[1]

A photosensitive resin composition for an organic EL element barrier rib comprising:

(A) a binder resin;

(B) at least one low molecular weight organic compound having a molar volume of 130 cm³/mol or less and being selected from the group consisting of aromatic carboxylic acids and compounds each having a plurality of phenolic hydroxyl groups;

(C) a radiation sensitive compound; and

(D) a colorant selected from the group consisting of black dyes and black pigments.

[2]

The photosensitive resin composition according to [1] wherein the low molecular weight organic compound (B) is an aromatic carboxylic acid having a pKa of 2.5 to 4.5.

[3]

The photosensitive resin composition according to [1] or [2] wherein the low molecular weight organic compound (B) is a compound having a plurality of phenolic hydroxyl groups and having a pKa of 7.5 to 10.

[4]

The photosensitive resin composition according to any one of [1] to [3] wherein a group other than carboxyl groups and phenolic hydroxyl groups is not bound to the carbon atoms constituting the aromatic ring of the low molecular weight organic compound (B).

[5]

The photosensitive resin composition according to any one of [1] to [4] wherein the compound having a plurality of phenolic hydroxyl groups is an aromatic polyol selected from the group consisting of catechol, resorcinol, hydroquinone, 1,2,4-benzenetriol, pyrogallol and phloroglucinol.

[6]

The photosensitive resin composition according to any one of [1] to [5] wherein the aromatic carboxylic acid is a polycarboxylic acid selected from the group consisting of phthalic acid, isophthalic acid, terephthalic acid, hemimellitic acid, trimellitic acid, and trimesic acid; or an aromatic hydroxycarboxylic acid selected from the group consisting of 2,3-dihydroxybenzoic acid, 2,4-dihydroxybenzoic acid, 2,5-dihydroxybenzoic acid, 3,5-dihydroxybenzoic acid, 2,3,4-trihydroxybenzoic acid, and gallic acid.

[7]

The photosensitive resin composition according to any one of [1] to [6] comprising 0.1 parts by mass to 20 parts by mass of the low molecular weight organic compound (B) with respect to 100 parts by mass of the total of the binder resin (A), the low molecular weight organic compound (B), the radiation sensitive compound (C), and the colorant (D).

[8]

The photosensitive resin composition according to any one of [1] to [7] wherein the radiation sensitive compound (C) is at least one photoacid generator selected from the group consisting of quinone diazide compounds, sulfonium salts, phosphonium salts, diazonium salts, and iodonium salts.

[9]

The photosensitive resin composition according to any one of [1] to [8] wherein the binder resin (A) has an alkali-soluble functional group.

[10]

The photosensitive resin composition according to any one of [1] to [9] comprising 1 part by mass to 70 parts by mass of the colorant (D) with respect to 100 parts by mass of the total of the binder resin (A), the low molecular weight organic compound (B), the radiation sensitive compound (C), and the colorant (D).

[11]

The photosensitive resin composition according to any one of [1] to [10] comprising a photoacid generator as 5 parts by mass to 50 parts by mass of the radiation sensitive compound (C) with respect to 100 parts by mass of the total of the binder resin (A), the low molecular weight organic compound (B), the radiation sensitive compound (C), and the colorant (D).

[12]

The photosensitive resin composition according to any one of [1] to [11] wherein the optical density (OD value) of a cured coating of the photosensitive resin composition is at least 0.5 per μm of film thickness.

[13]

The photosensitive resin composition according to any one of [1] to [12] wherein the binder resin (A) comprises at least one selected from the group consisting of:

(a) a polyalkenylphenolic resin having a structural unit represented by formula (1)

wherein in formula (1), R¹, R², and R³ each independently represent a hydrogen atom; an alkyl group with 1 to 5 carbon atoms; an alkenyl group represented by formula (2)

wherein in formula (2), R⁶, R⁷, R⁸, R⁹, and R¹⁰ each independently represent a hydrogen atom, an alkyl group with 1 to 5 carbon atoms, a cycloalkyl group with 5 to 10 carbon atoms, or an aryl group with 6 to 12 carbon atoms, the * in formula (2) represents the bond with the carbon atom constituting the aromatic ring; an alkoxy group with 1 or 2 carbon atoms; or a hydroxyl group, and at least one of R¹, R² and R³ is the alkenyl group represented by formula (2), Q is an alkylene group represented by the formula —CR⁴R⁵—, a cycloalkylene group with 5 to 10 carbon atoms, a divalent organic group having an aromatic ring, a divalent organic group having an alicyclic fused ring, or a divalent group consisting of a combination thereof, R⁴ and R⁵ each independently represent a hydrogen atom, an alkyl group with 1 to 5 carbon atoms, an alkenyl group with 2 to 6 carbon atoms, a cycloalkyl group with 5 to 10 carbon atoms or an aryl group with 6 to 12 carbon atoms; (b) a hydroxypolystyrene resin derivative having a structural unit represented by formula (3)

wherein in formula (3), R¹¹ is a hydrogen atom or an alkyl group with 1 to 5 carbon atoms, a is an integer from 1 to 4, b is an integer from 1 to 4, a+b is within the range of 2 to 5, R¹² is at least one selected from the group consisting of a hydrogen atom, a methyl group, an ethyl group and a propyl group; (c) an aqueous alkaline solution-soluble resin having an epoxy group and a phenolic hydroxyl group; and (d) an aqueous alkaline solution-soluble copolymer of a polymerizable monomer having an alkali-soluble functional group and an additional polymerizable monomer. [14]

An organic EL element barrier rib comprising a cured product of the photosensitive resin composition according to any one of [1] to [13].

[15]

An organic EL element comprising a cured product of the photosensitive resin composition according to any one of [1] to [13].

Advantageous Effects of Invention

According to the present disclosure, a highly sensitive colorant-containing photosensitive resin composition to be used for the formation of organic EL element barrier ribs can be provided.

DESCRIPTION OF EMBODIMENTS

The present invention will be described in more detail below.

“Alkali-soluble” as used herein refers to a photosensitive resin composition or a coating or cured coating thereof that can dissolve in an aqueous alkaline solution, for example, an aqueous solution of 2.38% by mass of tetramethylammonium hydroxide. “Alkali-soluble functional group” refers to a group that imparts such alkali-solubility to a photosensitive resin composition or a coating or cured coating thereof.

“Radical polymerizable functional group” as used herein refers to one or more ethylenically unsaturated groups, and “radical polymerizable compound” refers to a compound having one or more ethylenically unsaturated groups.

“(Meth)acrylic” as used herein refers to acrylic or methacrylic, and “(meth)acrylate” refers to acrylate or methacrylate.

In one embodiment, the photosensitive resin composition comprises: (A) a binder resin; (B) at least one low molecular weight organic compound having a molar volume of 130 cm³/mol or less and being selected from the group consisting of aromatic carboxylic acids and compounds each having a plurality of phenolic hydroxyl groups; (C) a radiation sensitive compound; and (D) a colorant selected from the group consisting of a black dye and a black pigment.

(A) Binder Resin

Binder resin (A) is not particularly limited but preferably has an alkali-soluble functional group and is alkali soluble. The alkali-soluble functional group is not particularly limited but may be a carboxyl group, a phenolic hydroxyl group, a sulfo group, a phosphoric acid group or a mercapto group. A binder resin comprising two or more alkali-soluble functional groups may be used.

Examples of the binder resin (A) include an acrylic resin, a polystyrene resin, an epoxy resin, a polyamide resin, a phenol resin, a polyimide resin, a polyamic acid resin, a polybenzoxazole resin, a polybenzoxazole resin precursor, a silicone resin, a cyclic olefin polymer, a cardo resin, and resins derived therefrom, and resins obtained by bonding an alkali-soluble functional group thereto. A homopolymer or copolymer of a polymerizable monomer having an alkali-soluble functional group may be used as the binder resin (A). These resins may be used independently or as a combination of two or more types of resin. The binder (A) may have a radical polymerizable functional group. In one embodiment, the binder resin (A) has a (meth)acrylic group, an allyl group, or a methallyl group as the radical polymerizable functional group.

In one embodiment, the binder resin (A) comprises at least one selected from the group consisting of the resin components (a) to (k) below.

-   (a) a polyalkenylphenolic resin -   (b) a hydroxypolystyrene resin derivative -   (c) an aqueous alkaline solution-soluble resin having an epoxy group     and a phenolic hydroxyl group -   (d) an aqueous alkaline solution-soluble copolymer of a     polymerizable monomer having an alkali-soluble functional group and     an additional polymerizable monomer -   (e) a polyimide resin -   (f) a polyamic acid resin -   (g) a polybenzoxazole resin -   (h) a polybenzoxazole resin precursor -   (i) a silicone resin -   (j) a cyclic olefin polymer -   (k) a cardo resin     (a) Polyalkenylphenolic Resin

The polyalkenylphenolic resin can be obtained by performing alkenyl etherification of the hydroxyl group of a known phenolic resin then further performing Claisen rearrangement on the alkenyl ether group. Thereamong, those with a structural unit represented by formula (1) are preferable.

By including such a resin, the development characteristics are improved and outgassing can be reduced in the obtained photosensitive resin composition.

In formula (1), R¹, R², and R³ each independently represent a hydrogen atom; an alkyl group with 1 to 5 carbon atoms; an alkenyl group represented by formula (2),

wherein in formula (2), R⁶, R⁷, R⁸, R⁹, and R¹⁰ each independently represent a hydrogen atom, an alkyl group with 1 to 5 carbon atoms, a cycloalkyl group with 5 to 10 carbon atoms, or an aryl group with 6 to 12 carbon atoms, the * in formula (2) represents the bond with the carbon atom constituting the aromatic ring; an alkoxy group with 1 or 2 carbon atoms; or a hydroxyl group, and at least one of R¹, R², and R³ is the alkenyl group represented by formula (2), Q is an alkylene group represented by the formula —CR⁴R⁵—, a cycloalkylene group with 5 to 10 carbon atoms, a divalent organic group having an aromatic ring, a divalent organic group having an alicyclic fused ring, or a divalent group consisting of a combination thereof, R⁴ and R⁵ each independently represent a hydrogen atom, an alkyl group with 1 to 5 carbon atoms, an alkenyl group with 2 to 6 carbon atoms, a cycloalkyl group with 5 to 10 carbon atoms or an aryl group with 6 to 12 carbon atoms. When two or more structural units represented by formula (1) are present in one molecule, the structural units represented by formula (1) may be the same or different for each one.

In formula (1), R¹, R², and R³ each independently represent a hydrogen atom, an alkyl group with 1 to 5 carbon atoms, an alkenyl group represented by formula (2), an alkoxy group with 1 or 2 carbon atoms, or a hydroxyl group, and at least one of R¹, R², and R³ is the alkenyl group represented by formula (2). Specific examples of the alkyl group with 1 to 5 carbon atoms represented by R¹, R², or R³ of formula (1) include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, a t-butyl group, and an n-pentyl group. Specific examples of the alkoxy group with 1 or 2 carbon atoms include a methoxy group and an ethoxy group.

R⁶, R⁷, R⁸, R⁹, and R¹⁰ in the alkenyl group represented by formula (2) each independently represent a hydrogen atom, an alkyl group with 1 to 5 carbon atoms, a cycloalkyl group with 5 to 10 carbon atoms, or an aryl group with 6 to 12 carbon atoms. Specific examples of the alkyl group with 1 to 5 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, a t-butyl group, and an n-pentyl group. Examples of the cycloalkyl group with 5 to 10 carbon atoms include a cyclopentyl group, a cyclohexyl group, a methylcyclohexyl group, and a cycloheptyl group. Specific examples of the aryl group with 6 to 12 carbon atoms include a phenyl group, a methylphenyl group, an ethylphenyl group, a biphenyl group, and a naphthyl group. It is preferable that R⁶, R⁷, R⁸, R⁹, and R¹⁰ each independently represent a hydrogen atom or an alkyl group with 1 to 5 carbon atoms. The alkenyl group represented by formula (2) is preferably an allyl group or a methallyl group from the standpoint of reactivity, and more preferably an allyl group.

It is most preferable that from among R¹, R², and R³, any one thereof is an allyl group or a methallyl group, and the other two are hydrogen atoms.

Q of formula (1) is an alkylene group represented by the formula —CR⁴R⁵—, a cycloalkylene group with 5 to 10 carbon atoms, a divalent organic group having an aromatic ring, a divalent organic group having an alicyclic fused ring, or a divalent group consisting of a combination thereof. R⁴ and R⁵ each independently represent a hydrogen atom, an alkyl group with 1 to 5 carbon atoms, an alkenyl group with 2 to 6 carbon atoms, a cycloalkyl group with 5 to 10 carbon atoms or an aryl group with 6 to 12 carbon atoms. Specific examples of the alkyl group with 1 to 5 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, a t-butyl group, and an n-pentyl group. Specific examples of the alkenyl group with 2 to 6 carbon atoms include a vinyl group, an allyl group, a butenyl group, a pentenyl group, and a hexenyl group. Examples of the cycloalkyl group with 5 to 10 carbon atoms include a cyclopentyl group, a cyclohexyl group, a methylcyclohexyl group, and a cycloheptyl group. Specific examples of the aryl group with 6 to 12 carbon atoms include a phenyl group, a methylphenyl group, an ethylphenyl group, a biphenyl group, and a naphthyl group. It is preferable that R⁴ and R⁵ each independently represent a hydrogen group or an alkyl group with 1 to 3 carbon atoms and it is most preferable for both to be hydrogen atoms.

Specific examples of the cycloalkylene group with 5 to 10 carbon atoms include a cyclopentylene group, a cyclohexylene group, a methylcyclohexylene group, and a cycloheptylene group. Specific examples of the divalent organic group having an aromatic ring include a phenylene group, a tolylene group, a naphthylene group, a biphenylene group, a fluorenylene group, an anthracenylene group, a xylylene group, a 4,4-methylene diphenyl group and a group represented by formula (6).

Specific examples of the divalent organic group having an alicyclic fused ring include a dicyclopentadienylene group.

When a polyalkenylphenolic resin is used as the binder resin (A), the polyalkenylphenolic resin which is particularly favorable in terms of alkali developability, outgassing, etc., may have a structural unit represented by formula (1) wherein Q is —CH₂—, i.e., represented by formula (4).

In formula (4), R¹, R², and R³ are the same as in formula (1). Preferable groups for R¹, R², and R³ are the same as those that are preferable in formula (1).

The structural unit represented by formula (1) or formula (4) is preferably included in the polyalkenylphenolic resin at 50 mol % to 100 mol %, more preferably 70 mol % to 100 mol % and even more preferably 80 mol % to 100 mol %. At least 50 mol % of the structural unit represented by formula (1) or formula (4) in the polyalkenylphenolic resin is favorable in terms of increasing heat resistance. The phenolic hydroxyl group in the polyalkenylphenolic resin ionizes in the presence of a basic compound, and the polyalkenylphenolic resin becomes soluble in water. Thus, at least a certain amount of phenolic hydroxyl groups is necessary from the standpoint of alkali developability. Accordingly, it is particularly favorable for the polyalkenylphenolic resin having a structural unit represented by formula (4) to be a polyalkenylphenolic resin having a structural unit represented by formula (4) and a structural unit represented by formula (7).

In formula (7), R^(1a), R^(2a), and R^(3a) each independently represent a hydrogen atom or an alkyl group with 1 to 5 carbon atoms. Preferable groups for R^(1a), R^(2a), and R^(3a) are the same as those for R¹, R², and R³ of formula (1).

In polyalkenylphenolic resins having a structural unit represented by formula (4) and a structural unit represented by formula (7), when x is the number of structural units represented by formula (4) and y is the number of structural units represented by formula (7), then 0.5≤x/(x+y)<1, and 0<y/(x+y)≤0.5, and x+y is preferably 2 to 50, more preferably 3 to 40 and even more preferably 5 to 25.

When a polyalkenylphenolic resin is used as the binder resin (A), the number average molecular weight of the polyalkenylphenolic resin is preferably 500 to 5000, more preferably 800 to 3000, and even more preferably 900 to 2000. Provided the number average molecular weight is at least 500, the alkali development rate is suitable and the difference in dissolution rate between light exposed and non-light exposed parts is sufficient for good pattern resolution. Provided the number average molecular weight is 5000 or less, alkali developability is good. Herein, the number average molecular weight and the weight average molecular weight of the binder resin (A) refer to standard polystyrene equivalent molecular weights measured by gel permeation chromatography (GPC).

(b) Hydroxypolystyrene Resin Derivative

A hydroxypolystyrene resin derivative having a structural unit represented by formula (3) can also be used for the binder resin (A).

The inclusion of such a resin improves the development characteristics of the photosensitive resin composition and can also contribute to the reduction of outgassing thereof.

In formula (3), R¹¹ represents a hydrogen atom or an alkyl group with 1 to 5 carbon atoms, a is an integer from 1 to 4, b is an integer from 1 to 4, a+b is in the range of 2 to 5, and R¹² is at least one selected from the group consisting of a hydrogen atom, a methyl group, an ethyl group, and a propyl group.

When a hydroxypolystyrene resin derivative is used as the binder resin (A), a copolymer comprising the structural unit represented by formula (3) and the structural unit represented by formula (5) is preferable in terms of alkali developability and outgassing.

In formula (5), R¹³ represents a hydrogen atom or an alkyl group with 1 to 5 carbon atoms and c is an integer from 1 to 5.

The hydroxypolystyrene resin derivative having a structural unit represented by formula (3) and the hydroxypolystyrene resin derivative having a structural unit represented by formula (3) and a structural unit represented by formula (5) can be obtained by, for example, polymerizing, using a publicly-known method, one or more phenolic hydroxyl group-containing aromatic vinyl compounds, such as p-hydroxystyrene, m-hydroxystyrene, o-hydroxystyrene, p-isopropenylphenol, m-isopropenylphenol, and o-isopropenylphenol, then reacting a portion of the obtained polymer or copolymer with formaldehyde using a publicly-known method or by further reacting with an alcohol.

p-Hydroxystyrene or m-hydroxystyrene may be favorably used for the phenolic hydroxyl group-containing aromatic vinyl compound.

When a hydroxypolystyrene resin derivative is used as the binder resin (A), the number average molecular weight of the hydroxypolystyrene resin derivative is preferably 1,000 to 20,000, more preferably 3,000 to 10,000, and even more preferably 4,000 to 9,000. Provided the number average molecular weight is at least 1,000, the use of the resin as a photosensitive material is favorable as the alkali solubility is suitable and provided the number average molecular weight is 20,000 or less, the coatability and developability is good.

(c) Aqueous Alkaline Solution-Soluble Resin Having an Epoxy Group and a Phenolic Hydroxyl Group

An aqueous alkaline solution-soluble resin having an epoxy group and a phenolic hydroxyl group may be used as the binder resin (A). Such an aqueous alkaline solution-soluble resin can be obtained by, for example, reacting epoxy groups of a compound having at least two epoxy groups per molecule (hereinafter may be referred to as “epoxy compound”) with the carboxyl group of a hydroxybenzoic acid compound. By having epoxy groups in the aqueous alkaline solution-soluble resin, crosslinking is formed during heating by reacting the epoxy groups with phenolic hydroxyl groups, whereby chemical resistance, heat resistance, etc., of the coating can be improved. The phenolic hydroxyl groups contribute to solubility in an aqueous alkaline solution during development.

The following reaction formula 1 is an example of a reaction in which one epoxy group of an epoxy compound and the carboxyl group of a hydroxybenzoic acid compound are reacted to form a phenolic hydroxyl group-containing compound.

Examples of the compound having at least two epoxy groups per molecule include an epoxy phenol novolak resin, an epoxy cresol novolak resin, a bisphenol epoxy resin, a biphenol epoxy resin, a naphthalene skeleton-containing epoxy resin, an alicyclic epoxy resin, and a heterocyclic epoxy resin. These epoxy compounds are acceptable provided there are at least two epoxy groups per molecule and one type may be used or a combination of two or more types may be used. As these are thermosetting compounds, the structures thereof cannot be unambiguously defined due to differences, such as the presence or absence of epoxy groups, the types of functional groups, and the degrees of polymerization, as is common knowledge for a person skilled in the art. One example of the structure of the epoxy novolak resin is illustrated in formula (9). In formula (9), R¹⁴ represents, for example, a hydrogen atom, an alkyl group with 1 to 5 carbon atoms, an alkoxy group with 1 or 2 carbon atoms or a hydroxyl group, and m is an integer from 1 to 50.

The epoxy phenolic novolak resin may be, for example, EPICLON® N-770 (DIC Corporation), or jER®-152 (Mitsubishi Chemical Corporation). The epoxy cresol novolak resin may be, for example, EPICLON® N-695 (DIC corporation), or EOCN®-102S (Nippon Kayaku Co., Ltd.). The bisphenol epoxy resin may be, for example, a bisphenol-A epoxy resin, such as jER® 828, jER® 1001 (Mitsubishi Chemical Corporation), and YD-128 (trade name, Nippon Steel & Sumikin Chemical Co., Ltd.), or a bisphenol-F epoxy resin, such as jER® 806 (Mitsubishi Chemical Corporation), and YDF-170 (trade name, Nippon Steel & Sumikin Chemical Co., Ltd.). The biphenol epoxy resin may be, for example, jER® YX-4000 or jER® YL-6121H (Mitsubishi Chemical Corporation). The naphthalene skeleton-containing epoxy resin may be, for example, NC-7000 (trade name, Nippon Kayaku Co., Ltd.) or EXA-4750 (trade name, DIC Corporation). The alicyclic epoxy resin may be, for example, EHPE®-3150 (Daicel® Corporation). The heterocyclic epoxy resin may be, for example, TEPIC®, TEPIC-L, TEPIC-H, or TEPIC-S (Nissan Chemical Corporation).

It is preferable for the compound having at least two epoxy groups per molecule to be an epoxy cresol novolak resin. Photosensitive resin compositions including an aqueous alkaline solution-soluble resin having an epoxy group and a phenolic hydroxyl group, the resin derived from an epoxy cresol novolak resin, have excellent pattern formability, have alkali solubility that is easy to adjust, and exhibit little outgassing.

The hydroxybenzoic acid compound is a compound in which at least one of positions 2 to 6 of benzoic acid has been substituted with a hydroxyl group. Examples thereof include salicylic acid, 4-hydroxybenzoic acid, 2,3-dihydroxybenzoic acid, 2,4-dihydroxybenzoic acid, 2,5-dihydroxybenzoic acid, 2,6-dihydroxybenzoic acid, 3,4-dihydroxybenzoic acid, 3,5-dihydroxybenzoic acid, 2-hydroxy-5-nitrobenzoic acid, 3-hydroxy-4-nitrobenzoic acid, and 4-hydroxy-3-nitrobenzoic acid. From the standpoint of increasing alkali developability, dihydroxybenzoic acid compounds are preferable. These hydroxybenzoic acid compounds may be used individually or in a combination of two or more.

In one embodiment, the aqueous alkaline solution-soluble resin having an epoxy group and a phenolic hydroxyl group is the reaction product of a compound having at least two epoxy groups per molecule and a hydroxybenzoic acid compound and has a structure represented by formula (8).

In formula (8), d is an integer from 1 to 5, * represents the bonding part to the residue derived by removing an epoxy group of the compound having at least two epoxy groups per molecule.

In a method for obtaining an aqueous alkaline solution-soluble resin having an epoxy group and a phenolic hydroxyl group from an epoxy compound and a hydroxybenzoic acid compound, with respect to one equivalent of epoxy groups of the epoxy compound, 0.2 to 1.0 equivalents of the hydroxybenzoic acid compound may be used, preferably 0.3 to 0.9 equivalents, and more preferably 0.4 to 0.8 equivalents. Sufficient alkali solubility can be attained with 0.2 equivalents or more of the hydroxybenzoic acid compound and 1.0 equivalents or less can suppress the increase in molecular weight due to side reactions.

A catalyst may be used to promote the reaction between the epoxy compound and the hydroxybenzoic acid compound. With respect to 100 parts by mass of the mixture of reactants including the epoxy compound and the hydroxybenzoic acid compound, the amount of catalyst to be used may be 0.1 to 10 parts by mass. The reaction temperature may be set to 60 to 150° C. and the reaction time may be set to 3 to 30 hours. The catalyst for use in this reaction may be, for example, triethylamine, benzyldimethylamine, triethylammonium chloride, benzyltrimethylammonium bromide, benzyltrimethylammonium iodide, triphenylphosphine, chromium octanoate, or zirconium octanoate.

The aqueous alkaline solution-soluble resin having an epoxy group and a phenolic hydroxyl group has a number average molecular weight of preferably 500 to 8,000, more preferably 800 to 6,000, and even more preferably 1,000 to 5,000. Provided the number average molecular weight is at least 500, the alkali solubility is appropriate and so the use of the resin as a photosensitive material is favorable, and provided the number average molecular weight is 8,000 or less, the coatability and developability are good.

(d) Aqueous Alkaline Solution-Soluble Copolymer of a Polymerizable Monomer Having an Alkali-Soluble Functional Group and an Additional Polymerizable Monomer

An aqueous alkaline solution-soluble copolymer of a polymerizable monomer having an alkali-soluble functional group and an additional polymerizable monomer may be used for the binder resin (A). The alkali-soluble functional group may be a carboxyl group, an alcoholic hydroxyl group, a phenolic hydroxyl group, a sulfo group, a phosphoric acid group, an acid anhydride group, etc. The polymerizable functional group of the polymerizable monomer may be a radical polymerizable functional group, such as CH₂═CH—, CH₂═C(CH₃)—, CH₂═CHCO—, CH₂═C(CH₃)CO—, or —OC—CH═CH—CO—.

The aqueous alkaline solution-soluble copolymer of a polymerizable monomer having an alkali-soluble functional group and an additional polymerizable monomer can be produced by, for example, the radical polymerization of an alkali soluble functional group-containing polymerizable monomer and an additional polymerizable monomer. A derivative obtained by synthesizing a copolymer by radical polymerization and thereafter adding an alkali-soluble functional group thereto may be used. Examples of the polymerizable monomer having an alkali-soluble functional group include 4-hydroxystyrene, (meth)acrylic acid, α-bromo(meth)acrylic acid, α-chloro(meth)acrylic acid, β-furyl(meth)acrylic acid, β-styryl(meth)acrylic acid, maleic acid, monomethyl maleate, monoethyl maleate, monoisopropyl maleate, fumaric acid, cinnamic acid, α-cyanocinnamic acid, itaconic acid, crotonic acid, propiolic acid, 4-hydroxyphenyl methacrylate, 3,5-dimethyl-4-hydroxybenzyl acrylamide, 4-hydroxyphenyl acrylamide, 4-hydroxyphenyl maleimide, 3-maleimidopropionic acid, 4-maleimidobutyric acid, and 6-maleimidohexanoic acid. Examples of the additional polymerizable monomer include polymerizable styrene derivatives, such as styrene, vinyl toluene, α-methylstyrene, p-methylstyrene, p-ethylstyrene; acrylamide; acrylonitrile; ether compounds of vinyl alcohol, such as n-butyl vinyl ether; (meth)acrylic acid esters, such as alkyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, glycidyl (meth)acrylate; 2,2,2-trifluoroethyl (meth)acrylate, 2,2,3,3-tetrafluoropropyl (meth)acrylate, isobornyl (meth)acrylate, maleic anhydride, maleic acid monoester; and N-substituted maleimides, such as phenylmaleimide and cyclohexyl maleimide. From the standpoint of heat resistance, the aqueous alkaline solution-soluble copolymer of a polymerizable monomer having an alkali-soluble functional group and an additional polymerizable monomer preferably has one or more cyclic structures, such as an alicyclic structure, an aromatic structure, a polycyclic structure, an inorganic cyclic structure, or a heterocyclic structure.

The polymerizable monomer having an alkali-soluble functional group preferably forms the structural unit represented by formula (10).

In formula (10), R¹⁵ represents a hydrogen atom or an alkyl group with 1 to 5 carbon atoms and e is an integer from 1 to 5. 4-Hydroxyphenyl methacrylate is particularly preferable for the polymerizable monomer having an alkali-soluble functional group.

The additional polymerizable monomer preferably forms the structural unit represented by formula (11).

In formula (11), R¹⁶ and R¹⁷ each independently represent a hydrogen atom, an alkyl group with 1 to 3 carbon atoms, a fully or partially fluorinated alkyl group with 1 to 3 carbon atoms, or a halogen atom. R¹⁸ represents a hydrogen atom, a linear or cyclic alkyl group with 1 to 6 carbon atoms, or a phenyl group, or represents a phenyl group substituted with at least one selected from the group consisting of a hydroxyl group, an alkyl group with 1 to 6 carbon atoms, and an alkoxy group with 1 to 6 carbon atoms. From such additional polymerizable monomers, phenyl maleimide and cyclohexyl maleimide are particularly preferable.

In one embodiment, the aqueous alkaline solution-soluble copolymer of a polymerizable monomer having an alkali-soluble functional group and an additional polymerizable monomer (d) has a structural unit represented by formula (10)

wherein in formula (10), R¹⁵ is a hydrogen atom or an alkyl group with 1 to 5 carbon atoms and e is an integer from 1 to 5, and a structural unit represented by formula (11)

wherein in formula (11), R¹⁶ and R¹⁷ each independently represent a hydrogen atom, an alkyl group with 1 to 3 carbon atoms, a fully or partially fluorinated alkyl group with 1 to 3 carbon atoms, or a halogen atom, and R¹⁸ represents a hydrogen atom, a linear or cyclic alkyl group with 1 to 6 carbon atoms or a phenyl group, or represents a phenyl group substituted with at least one selected from the group consisting of a hydroxyl group, an alkyl group with 1 to 6 carbon atoms, and an alkoxy group with 1 to 6 carbon atoms.

It is particularly preferable that 4-hydroxyphenyl methacrylate be used for the polymerizable monomer having an alkali-soluble functional group, and phenyl maleimide or cyclohexyl maleimide be used for the additional polymerizable monomer. Shape retainability and developability can be improved and outgassing can be reduced by using a resin obtained by radical polymerizing these polymerizable monomers.

Examples of the polymerization initiator used when producing the aqueous alkaline solution-soluble copolymer of a polymerizable monomer having an alkali-soluble functional group and an additional polymerizable monomer by radical polymerization include, but not limited to, azo polymerization initiators, such as 2,2′-azobisisobutyronitrile, 2,2′-azobis(2-methylbutyronitrile), dimethyl 2,2′-azobis(2-methylpropionate), 4,4′-azobis(4-cyanovaleric acid), and 2,2′-azobis(2,4-dimethyl valeronitrile) (AVN); peroxide polymerization initiators with a 10 hour half-life temperature of 100 to 170° C., such as dicumyl peroxide, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, tert-butylcumyl peroxide, di-tert-butyl peroxide, 1,1,3,3-tetramethyl butyl hydroperoxide, and cumene hydroperoxide; and peroxide polymerization initiators, such as benzoyl peroxide, lauroyl peroxide, 1,1′-di(t-butylperoxy)cyclohexane, and t-butyl peroxypivalate. The amount of the polymerization initiator used with respect to 100 parts by mass of the polymerizable monomer mixture is, in general, preferably 0.01 parts by mass or more, 0.05 parts by mass or more or 0.5 parts by mass or more, 40 parts by mass or less, 20 parts by mass or less or 15 parts by mass or less.

A RAFT (Reversible Addition Fragmentation Transfer) agent may be used in combination with the polymerization initiator. Examples of the RAFT agent include, but not limited to, thiocarbonylthio compounds, such as dithioesters, dithiocarbamates, trithiocarbonates, and xanthates. With respect to 100 parts by mass of the total of the polymerizable monomers, the RAFT agent may be used in a range of 0.005 to 20 parts by mass, and preferably in the range of 0.01 to 10 parts by mass.

The weight average molecular weight (Mw) of the aqueous alkaline solution-soluble copolymer of a polymerizable monomer having an alkali-soluble functional group and an additional polymerizable monomer may be 3,000 to 80,000, preferably 4,000 to 70,000, and more preferably 5,000 to 60,000. The number average molecular weight (Mn) may be 1,000 to 30,000, preferably 1,500 to 25,000 and more preferably 2,000 to 20,000. The polydispersity index (Mw/Mn) may be 1.0 to 3.5, preferably 1.1 to 3.0, more preferably 1.2 to 2.8. Provided the weight average molecular weight, the number average molecular weight, and the polydispersity index are within the aforementioned ranges, a photosensitive resin composition with excellent alkali solubility and developability can be obtained.

Herein, if the aqueous alkaline solution-soluble copolymer of a polymerizable monomer having an alkali-soluble functional group and an additional polymerizable monomer (d) also corresponds to the hydroxypolystyrene resin derivative (b), the same will be treated as the aqueous alkaline solution-soluble copolymer of a polymerizable monomer having an alkali-soluble functional group and an additional polymerizable monomer (d). If the aqueous alkaline solution-soluble copolymer of a polymerizable monomer having an alkali-soluble functional group and an additional polymerizable monomer (d) also corresponds to the aqueous alkaline solution-soluble resin having an epoxy group and a phenolic hydroxyl group (c), the same will be treated as the aqueous alkaline solution-soluble copolymer of a polymerizable monomer having an alkali-soluble functional group and an additional polymerizable monomer (d). In other words, the hydroxypolystyrene resin derivative (b) and the aqueous alkaline solution-soluble resin having an epoxy group and a phenolic hydroxyl group (c) exclude those that correspond to the aqueous alkaline solution-soluble copolymer of a polymerizable monomer having an alkali-soluble functional group and an additional polymerizable monomer (d).

In one embodiment, the binder resin (A) includes a phenolic resin, such as a phenolic novolak resin, a cresol novolak resin, a triphenylmethane phenolic resin, a phenolic aralkyl resin, a biphenylaralkylphenolic resin, a phenol-dicyclopentadiene copolymer resin, or a derivative thereof. When a phenolic resin is used as the binder (A), a preferable number average molecular weight is generally 100 to 50,000, more preferably 500 to 30,000 and even more preferably 800 to 10,000, although this depends on the resin structure. Provided the number average molecular weight is at least 100, the rate of alkali development is suitable and as the difference in dissolution rate between the light exposed parts and the non-light exposed parts is sufficient, pattern resolution is good, and provided the number average molecular weight is 50,000 or less, the alkali developability is good.

(e) Polyimide Resin, (f) Polyamic Acid Resin, (g) Polybenzoxazole Resin and (h) Polybenzoxazole Resin Precursor

In one embodiment, the binder resin (A) is at least one selected from the group consisting of a polyimide resin (e), a polyamic acid resin (f), a polybenzoxazole resin (g), and a polybenzoxazole resin precursor (h). The dehydration and ring closure of the polyamic acid resin results in the formation of a resin having a polyimide structure. The dehydration and ring closure of the polybenzoxazole resin precursor results in the formation of a polybenzoxazole resin.

The polyimide resin (e) has a structural unit represented by formula (12). The polyamic acid resin (f) and the polybenzoxazole resin precursor (h) have a structural unit represented by formula (13). The polybenzoxazole resin (g) has a structural unit represented by formula (14). The polyimide resin may have both the structural unit represented by formula (12) and the structural unit represented by formula (13), and the polybenzoxazole resin may have both the structural unit represented by formula (14) and the structural unit represented by formula (13).

In formula (12), R¹⁹ represents a 4 to 10 valence organic group, R²⁰ represents a 2 to 8 valence organic group, and R²¹ and R²² each independently represent a hydroxyl group, a carboxyl group, a sulfo group or a mercapto group, and f and g are each independently an integer from 0 to 6.

In formula (13), R²³ represents a 2 to 8 valence organic group, R²⁴ represents a 2 to 8 valence organic group, R²⁵ and R²⁶ each independently represent a hydroxyl group, a sulfo group, a mercapto group, or —COOR²⁷ where R²⁷ represents a hydrogen atom or a monovalent hydrocarbon group with 1 to 20 carbon atoms, and h and i are each independently an integer from 0 to 6, provided that h+i>0. In the case of a polyamic acid resin, h is an integer of 1 or more and at least one R²⁵ is —COOR²⁷. In the case of a polybenzoxazole resin precursor, i is an integer of 1 or more and at least one R²⁶ is a phenolic hydroxyl group.

In formula (14), R²⁸ represents a 2 to 8 valence organic group, R²⁹ represents a 2 to 8 valence organic group, and R³⁰ and R³¹ each independently represent a hydroxyl group, a carboxyl group, a sulfo group or a mercapto group, and j and k are each independently an integer from 0 to 6.

R¹⁹—(R²¹)_(f) of formula (12) represent acid dianhydride residues. R¹⁹ is a 4 to 10 valence organic group and is preferably an aromatic ring- or a cyclic aliphatic group-containing organic group with 5 to 40 carbon atoms.

Examples of the acid dianhydride include: aromatic tetracarboxylic acid dianhydrides, such as pyromellitic dianhydride, 3,3′,4,4′-biphenyltetracarboxylic dianhydride, 2,3,3′,4′-biphenyltetracarboxylic dianhydride, 2,2′,3,3′-biphenyltetracarboxylic dianhydride, 3,3′,4,4′-benzophenonetetracarboxylic dianhydride, 2,2′,3,3′-benzophenonetetracarboxylic dianhydride, 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride, 2,2-bis(2,3-dicarboxyphenyl)propane dianhydride, 1,1-bis(3,4-dicarboxyphenyl)ethane dianhydride, 1,1-bis(2,3-dicarboxyphenyl)ethane dianhydride, bis(3,4-dicarboxyphenyl)methane dianhydride, bis(2,3-dicarboxyphenyl)methane dianhydride, bis(3,4-dicarboxyphenyl) ether dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride, 9,9-bis[4-(3,4-dicarboxyphenoxy)phenyl]fluorene dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 2,3,5,6-pyridinetetracarboxylic dianhydride, 3,4,9,10-perylenetetracarboxylic dianhydride, and 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride; aliphatic tetracarboxylic dianhydrides, such as butanetetracarboxylic dianhydride, and 1,2,3,4-cyclopentanetetracarboxylic dianhydride; and combinations of two or more thereof.

R²³—(R²⁵)_(h) of formula (13) and R²⁸—(R³⁰)_(i) of formula (14) each represent an acid residue. R²³ and R²⁸ each independently represent a 2 to 8 valence organic group and are preferably an aromatic ring- or cyclic aliphatic group-containing organic group with 5 to 40 carbon atoms.

Examples of the acid include: aromatic dicarboxylic acids, such as terephthalic acid, isophthalic acid, diphenyl ether dicarboxylic acid, bis(carboxyphenyl)hexafluoropropane, biphenyl dicarboxylic acid, benzophenone dicarboxylic acid, and triphenyl dicarboxylic acid; aromatic tricarboxylic acids, such as trimellitic acid, trimesic acid, diphenyl ether tricarboxylic acid, and biphenyl tricarboxylic acid; aromatic tetracarboxylic acids, such as pyromellitic acid, 3,3′,4,4′-biphenyltetracarboxylic acid, 2,3,3′,4′-biphenyltetracarboxylic acid, 2,2′,3,3′-biphenyltetracarboxylic acid, 3,3′,4,4′-benzophenonetetracarboxylic acid, 2,2′,3,3′-benzophenonetetracarboxylic acid, 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane, 2,2-bis(2,3-dicarboxyphenyl)hexafluoropropane, 1,1-bis(3,4-dicarboxyphenyl)ethane, 1,1-bis(2,3-dicarboxyphenyl)ethane, bis(3,4-dicarboxyphenyl)methane, bis(2,3-dicarboxyphenyl)methane, bis(3,4-dicarboxyphenyl) ether, 1,2,5,6-naphthalenetetracarboxylic acid, 2,3,6,7-naphthalenetetracarboxylic acid, 2,3,5,6-pyridinetetracarboxylic acid, and 3,4,9,10-perylenetetracarboxylic acid; aliphatic tetracarboxylic acids, such as butanetetracarboxylic acid, and 1,2,3,4-cyclopentanetetracarboxylic acid; and combinations of two or more thereof. In the aforementioned tricarboxylic acids and tetracarboxylic acids, one or two carboxyl groups correspond to R²⁵ of formula (13) and R³⁰ of formula (14). These acids may take the form of esters or acid anhydrides.

R²⁰—(R²²)_(g) of formula (12), R²⁴—(R²⁶)_(i) of formula (13), R²⁹—(R³¹)_(k) of formula (14) each represent a diamine residue. R²⁰, R²⁴, and R²⁹ each independently represent a 2 to 8 valence organic group, preferable an aromatic ring- or cyclic aliphatic group-containing organic group with 5 to 40 carbon atoms.

Examples of the diamine that corresponds to R²⁰ of formula (12) and R²⁴ of formula (13) related to the polyamic acid resin include: aromatic diamines, such as 3,4′-diaminodiphenyl ether, 4,4′-diaminodiphenyl ether, 3,4′-diaminodiphenylmethane, 4,4′-diaminodiphenylmethane, 1,4-bis(4-aminophenoxy)benzene, benzidine, m-phenylenediamine, p-phenylenediamine, 1,5-naphthalenediamine, 2,6-naphthalenediamine, bis(4-aminophenoxy)biphenyl, bis[4-(4-aminophenoxy)phenyl] ether, 1,4-bis(4-aminophenoxy)benzene, 2,2′-dimethyl-4, 4′-diaminobiphenyl, 2,2′-diethyl-4,4′-diaminobiphenyl, 3,3′-dimethyl-4,4′-diaminobiphenyl, 3,3′-diethyl-4,4′-diaminobiphenyl, 2,2′,3,3′-tetramethyl-4,4′-diaminobiphenyl, 3,3′,4,4′-tetramethyl-4,4′-diaminobiphenyl, 2,2′-di(trifluoromethyl)-4,4′-diaminobiphenyl, and 9,9-bis(4-aminophenyl) fluorene; compounds obtained by substituting at least one hydrogen atom on the aromatic ring of these aromatic diamines with an alkyl group or a halogen atom; aliphatic diamines, such as cyclohexyldiamine, and methylene biscyclohexylamine; and combinations of two or more thereof.

Examples of the diamine that corresponds to R²⁴ of formula (13) related to the polybenzoxazole resin precursor and R²⁹ of formula (14) include bisaminophenol compounds having a phenolic hydroxyl group at the ortho position with respect to the amino group on the aromatic ring of the aforementioned aromatic diamines and combinations of two or more thereof.

The terminal of the polyimide resin, polyamic acid resin, polybenzoxazole resin, and polybenzoxazole resin precursor may be capped with a monoamine, acid anhydride, acid chloride or monocarboxylic acid having an acidic group so that these resins have an acidic group at the terminal of the main chain thereof.

The polyamic acid resin may be synthesized by, for example: a method in which a tetracarboxylic dianhydride and a diamine are reacted; a method in which a diester is formed from a tetracarboxylic dianhydride and an alcohol and thereafter the diester is reacted with a diamine in the presence of a condensing agent; or a method in which a diester is formed from the tetracarboxylic dianhydride and alcohol, the remaining dicarboxylic acid is reacted to form acid chloride, and the obtained intermediate is reacted with a diamine.

The polybenzoxazole resin precursor can be synthesized by, for example, a condensation reaction in which a bisaminophenol compound is reacted with a polycarboxylic acid, such as a dicarboxylic acid, a tricarboxylic acid, or a tetracarboxylic acid. Specific examples include: a method in which an intermediate obtained by reacting a dehydrating condensing agent, such as dicyclohexyl carbodiimide (DCC), with a polycarboxylic acid is reacted with a bisaminophenol compound; and a method in which a dicarboxylic acid dichloride solution is dripped into a solution of a bisaminophenol compound to which a tertiary amine, such as pyridine, is added.

The polyimide resin can be synthesized by, for example, the dehydration and ring closure of a polyamic acid resin obtained in the aforementioned method by heating or chemical treatment thereof with an acid, a base, etc.

The polybenzoxazole resin can be synthesized by, for example, the dehydration and ring closure of the polybenzoxazole resin precursor obtained in the aforementioned method by heating or chemical treatment thereof with an acid, a base, etc.

The number average molecular weight of the polyimide resin, polyamic acid resin, polybenzoxaxole resin, and polybenzoxazole resin precursor is preferably 500 to 8,000, more preferably 800 to 6,000, and even more preferably 1,000 to 5,000. Provided the number average molecular weight is at least 500, the use of the resin as a photosensitive material is favorable as the alkali solubility is suitable, and provided the number average molecular weight is 8,000 or less, the coatability and developability are good.

(i) Silicone Resin

In one embodiment, the binder resin (A) includes a silicone resin (i). The silicone resin can be synthesized by the hydrolytic condensation of at least one compound selected from the group consisting of an organosilane represented by formula (15) and an organosilane represented by formula (16). By using the organosilanes represented by formula (15) or formula (16), a photosensitive resin composition with excellent sensitivity and resolution can be obtained.

The organosilane represented by formula (15) is shown below. (R³²)_(p)Si(OR³³)_(4-p)  (15)

In formula (15), R³² represents a hydrogen atom, an alkyl group with 1 to 10 carbon atoms, an alkenyl group with 2 to 10 carbon atoms, or an aryl group with 6 to 16 carbon atoms; R³³ represents a hydrogen atom, an alkyl group with 1 to 6 carbon atoms, an acyl group with 2 to 6 carbon atoms, or an aryl group with 6 to 16 carbon atoms; and p is an integer of 0 to 3. When p is two or more, the plurality of R³²s may each be the same or different. When p is two or less, the plurality of R³³s may each be the same or different.

Examples of the organosilane represented by formula (15) include: tetrafunctional silanes, such as tetramethoxysilane, tetraethoxysilane, tetraacetoxysilane, and tetraphenoxysilane; trifunctional silanes, such as methyltrimethoxysilane, methyltriethoxysilane, methyltriisopropoxysilane, methyltri-n-butoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, ethyltriisopropoxysilane, ethyltri-n-butoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, n-butyltrimethoxysilane, n-butyltriethoxysilane, n-hexyltrimethoxysilane, n-hexyltriethoxysilane, decyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, p-hydroxyphenyltrimethoxysilane, 1-(p-hydroxyphenyl)ethyltrimethoxysilane, 2-(p-hydroxyphenyl)ethyltrimethoxysilane, 4-hydroxy-5-(p-hydroxyphenylcarbonyloxy)pentyltrimethoxysilane, trifluoromethyltrimethoxysilane, trifluoromethyltriethoxysilane, 3,3,3-trifluoropropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane, [(3-ethyl-3-oxetanyl)methoxy]propyltrimethoxysilane, [(3-ethyl-3-oxetanyl)methoxy]propyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-trimethoxysilylpropylsuccinic acid, 1-naphthyltrimethoxysilane, 1-naphthyltriethoxysilane, 1-naphthyltri-n-propoxysilane, 2-naphthyltrimethoxysilane, 1-anthracenyltrimethoxysilane, 9-anthracenyltrimethoxysilane, 9-phenanthrenyltrimethoxysilane, 9-fluorenyltrimethoxysilane, 2-fluorenyltrimethoxysilane, 1-pyrenyltrimethoxysilane, 2-indenyltrimethoxysilane, and 5-acenaphthenyltrimethoxysilane; bifunctional silanes, such as dimethyldimethoxysilane, dimethyldiethoxysilane, dimethyldiacetoxysilane, di-n-butyldimethoxysilane, diphenyldimethoxysilane, (3-glycidoxypropyl)methyldimethoxysilane, (3-glycidoxypropyl)methyldiethoxysilane, di(1-naphthyl)dimethoxysilane, di(1-naphthyl)diethoxysilane; monofunctional silanes, such as trimethylmethoxysilane, tri-n-butylethoxysilane, (3-glycidoxypropyl)dimethylmethoxysilane, and (3-glycidoxypropyl)dimethylethoxysilane; and combinations of two or more thereof.

The organosilane represented by formula (16) is shown below.

In formula (16), R³⁴ to R³⁷ each independently represent a hydrogen atom, an alkyl group with 1 to 6 carbon atoms, an acyl group with 2 to 6 carbon atoms or an aryl group with 6 to 16 carbon atoms, and n is in the range of 2 to 8. When n is two or more, the plurality of R³⁵s and R³⁶s may be the same or different.

Specific examples of the organosilane represented by formula (16) include: methyl silicate 51 (R³⁴ to R³⁷ are methyl groups and n is an average of 4) manufactured by Fuso Chemical Co., Ltd; M silicate 51 (R³⁴ to R³⁷ are methyl groups and n is an average of 3 to 5), silicate 40 (R³⁴ to R³⁷ are ethyl groups and n is an average of 4 to 6), and silicate 45 (R³⁴ to R³⁷ are ethyl groups and n is an average of 6 to 8) manufactured by Tama Chemicals Co., Ltd.; and methyl silicate 51 (R³⁴ to R³⁷ are methyl groups and n is an average of 4), methyl silicate 53A (R³⁴ to R³⁷ are methyl groups and n is an average of 7), ethyl silicate 40 (R³⁴ to R³⁷ are ethyl groups and n is an average of 5) manufactured by Colcoat Co., Ltd. A combination of two or more thereof may also be used.

The silicone resin can be synthesized by the hydrolysis and partial condensation of the organosilanes represented by formula (15) or formula (16). Partial condensation results in residual silanol groups being present in the silicone resin. Hydrolysis and partial condensation can be carried out by, for example, a method in which a solvent, water, a catalyst, etc., are added as necessary to the organosilane mixture which is then heated and stirred at a temperature of 50 to 150° C. for 0.5 to 100 hours. By-products of hydrolysis (alcohols, such as methanol) or by-products of condensation (water) may be evaporated off by distillation.

An acidic or basic catalyst is preferably used for the catalyst. Examples of the acidic catalyst include hydrochloric acid, nitric acid, sulfuric acid, hydrofluoric acid, phosphoric acid, acetic acid, trifluoroacetic acid, formic acid, a polycarboxylic acid and an anhydride thereof, and an ion exchange resin. Examples of the basic catalyst include triethylamine, tripropylamine, tributylamine, tripentylamine, trihexylamine, triheptylamine, trioctylamine, diethylamine, triethanolamine, diethanolamine, sodium hydroxide, potassium hydroxide, an alkoxysilane having an amino group, and an ion exchange resin. After hydrolysis and partial condensation have been carried out, the catalyst may be removed by washing with water, treating with an ion exchange resin, or a combination thereof as necessary. By removing the catalyst, the storage stability of the photosensitive resin composition can be increased.

The weight average molecular weight (Mw) of the silicone resin is preferably 1,000 to 100,000 and more preferably 1,000 to 50,000. Provided the weight average molecular weight is at least 1,000, the film formability can be improved, and provided the weight average molecular weight is 100,000 or less, the alkali developability is good.

(j) Cyclic Olefin Polymer

In one embodiment, the binder (A) includes a cyclic olefin polymer (j). The cyclic olefin polymer is a homopolymer or copolymer of a cyclic olefin monomer having a cyclic structure (alicyclic or aromatic) and a carbon-carbon double bond. The cyclic olefin polymer may have a structural unit derived from a monomer other than a cyclic olefin monomer.

Examples of the monomer constituting the cyclic olefin polymer include cyclic olefin monomers having a polar protic group, cyclic olefin monomers having a polar aprotic group, cyclic olefin monomers having no polar group, and monomers other than cyclic olefins. The monomers other than cyclic olefins may have a polar protic group or a polar group other than the polar protic group, or may have no polar group.

Examples of the cyclic olefin monomer having a polar protic group include: carboxyl group-containing cyclic olefins, such as 5-hydroxycarbonylbicyclo[2.2.1]hept-2-ene, 5-methyl-5-hydroxycarbonylbicyclo[2.2.1]hept-2-ene, 5-carboxymethyl-5-hydroxycarbonylbicyclo[2.2.1]hept-2-ene, 5-exo-6-endo-dihydroxycarbonylbicyclo[2.2.1]hept-2-ene, 8-hydroxycarbonyltetracyclo[4.4.0.1^(2,5).1^(7,10)]dodec-3-ene, 8-methyl-8-hydroxycarbonyltetracyclo[4.4.0.1^(2,5).1^(7,10)]dodec-3-ene, and 8-exo-9-endo-dihydroxycarbonyltetracyclo[4.4.0.1^(2,5).1^(7,10)]dodec-3-ene; hydroxyl group-containing cyclic olefins, such as 5-(4-hydroxyphenyl) bicyclo[2.2.1]hept-2-ene, 5-methyl-5-(4-hydroxyphenyl)bicyclo[2.2.1]hept-2-ene, 8-(4-hydroxyphenyl)tetracyclo[4.4.0.1^(2,5).1^(7,10)]dodec-3-ene, and 8-methyl-8-(4-hydroxyphenyl)tetracyclo[4.4.0.1^(2,5).1^(7,10)]dodec-3-ene; and combinations of two or more thereof.

Examples of the cyclic olefin monomer having a polar aprotic group include: cyclic olefins having an ester group, such as 5-acetoxybicyclo[2.2.1]hept-2-ene, 5-methoxycarbonylbicyclo[2.2.1]hept-2-ene, 5-methyl-5-methoxycarbonylbicyclo[2.2.1]hept-2-ene, 8-acetoxytetracyclo[4.4.0.1^(2,5).1^(7,10)]dodec-3-ene, 8-methoxycarbonyltetracyclo[4.4.0.1^(2,5).1^(7,10)]dodec-3-ene, 8-ethoxycarbonyltetracyclo[4.4.0.1^(2,5).1^(7,10)]dodec-3-ene, 8-n-propoxycarbonyltetracyclo[4.4.0.11^(2,5).1^(7,10)]dodec-3-ene, 8-isopropoxycarbonyltetracyclo[4.4.0.1^(2,5).1^(7,10)]dodec-3-ene, 8-n-butoxycarbonyltetracyclo[4.4.0.1^(2,5).1^(7,10)]dodec-3-ene, 8-methyl-8-methoxycarbonyltetracyclo[4.4.0.1^(2,5).1^(7,10)]dodec-3-ene, 8-methyl-8-ethoxycarbonyltetracyclo[4.4.0.1^(2,5).1^(7,10)]dodec-3-ene, 8-methyl-8-n-propoxycarbonyltetracyclo[4.4.0.1^(2,5).1^(7,10)]dodec-3-ene, 8-methyl-8-isopropoxycarbonyltetracyclo[4.4.0.1^(2,5).1^(7,10)]dodec-3-ene, 8-methyl-8-n-butoxycarbonyltetracyclo[4.4.0.1^(2,5).1^(7,10)]dodec-3-ene, 8-(2,2,2-trifluoroethoxycarbonyl)tetracyclo[4.4.0.1^(2,5).1^(7,10)]dodec-3-ene, and 8-methyl-8-(2,2,2-trifluoroethoxycarbonyl)tetracyclo[4.4.0.1^(2,5).1^(7,10)]dodec-3-ene; cyclic olefins having an N-substituted imide group, such as N-phenyl-(5-norbornene-2,3-dicarboximide); cyclic olefins having a cyano group, such as 8-cyanotetracyclo[4.4.0.1^(2,5).1^(7,10)]dodec-3-ene, 8-methyl-8-cyanotetracyclo[4.4.0.1^(2,5).1^(7,10)]dodec-3-ene, 5-cyanobicyclo[2.2.1]hept-2-ene; a cyclic olefin having a halogen atom, such as 8-chlorotetracyclo[4.4.0.1^(2,5).1^(7,10)]dodec-3-ene, and 8-methyl-8-chlorotetracyclo[4.4.0.1^(2,5).1^(7,10)]dodec-3-ene; and combinations of two or more thereof.

Examples of the cyclic olefin monomer having no polar group include: bicyclo[2.2.1]hept-2-ene, 5-ethyl-bicyclo[2.2.1]hept-2-ene, 5-butyl-bicyclo[2.2.1]hept-2-ene, 5-ethylidene-bicyclo[2.2.1]hept-2-ene, 5-methylidene-bicyclo[2.2.1]hept-2-ene, 5-vinyl-bicyclo[2.2.1]hept-2-ene, tricyclo[4.3.0.1^(2,5)]deca-3,7-diene, tetracyclo[8.4.0.1^(11,14).0^(3,7)]pentadeca-3,5,7,12,11-pentaene, tetracyclo[4.4.0.1^(2,5).1^(7,10)]dec-3-ene, 8-methyl-tetracyclo[4.4.0.1^(2,5).1^(7,10)]dodec-3-ene, 8-ethyl-tetracyclo[4.4.0.1^(2,5).1^(7,10)]dodec-3-ene, 8-methylidene-tetracyclo[4.4.0.1^(2,5).1^(7,10)]dodec-3-ene, 8-ethylidene-tetracyclo[4.4.0.1^(2,5).1^(7,10)]dodec-3-ene, 8-vinyl-tetracyclo[4.4.0.1^(2,5).1^(7,10)]dodec-3-ene, 8-propenyl-tetracyclo[4.4.0.1^(2,5).1^(7,10)]dodec-3-ene, pentacyclo[6.5.1.1^(3,6).0^(2,7).0^(9,13)]pentadeca-3,10-diene, cyclopentene, cyclopentadiene, 1,4-methano-1,4,4a, 5,10,10a-hexahydroanthracene, 8-phenyl-tetracyclo[4.4.0.1^(2,5).1^(7,10)]dodec-3-ene, tetracyclo[9.2.1.0^(2,10).0^(3,8)]tetradeca-3,5,7,12-tetraene, pentacyclo[7.4.0.1^(3,6).1^(10,13).0^(2,7)]pentadeca-4,11-diene, pentacyclo[9.2.1.14,7.0^(2,10).0^(3,8)]pentadeca-5,12-diene, and combinations of two or more thereof.

Specific examples of the monomer other than cyclic olefins include: α-olefins with 2 to 20 carbon atoms, such as ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 3-methyl-1-butene, 3-methyl-1-pentene, 3-ethyl-1-pentene, 4-methyl-1-pentene, 4-methyl-1-hexene, 4,4-dimethyl-1-hexene, 4,4-dimethyl-1-pentene, 4-ethyl-1-hexene, 3-ethyl-1-hexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, and 1-eicosene; linear olefins, such as non-conjugated dienes, such as 1,4-hexadiene, 4-methyl-1,4-hexadiene, 5-methyl-1,4-hexadiene, and 1,7-octadiene; and combinations of two or more thereof.

The cyclic olefin polymer can be synthesized by ring-opening polymerization or addition polymerization of the aforementioned monomers. For the polymerization catalyst, a metal complex of, for example, molybdenum, ruthenium or osmium or a combination of two or more thereof is preferably used. The cyclic olefin polymer may undergo hydrogenation treatment. A catalyst that is generally used for the hydrogenation of olefin compounds may be used as the hydrogenation catalyst, for example, a Ziegler-type homogeneous catalyst, a precious metal complex catalyst, or a supported precious metal catalyst.

The weight average molecular weight (Mw) of the cyclic olefin polymer is preferably 1,000 to 100,000, and more preferably 1,000 to 50,000. Provided the weight average molecular weight is 1,000 or more, the film formability can be improved, and provided the weight average molecular weight is 100,000 or less, the alkali developability is good.

(k) Cardo Resin

In one embodiment, the binder resin (A) includes a cardo resin (k). The cardo resin has a cardo structure, namely, a skeleton structure in which a quaternary carbon atom constituting a cyclic structure is bonded to two other cyclic structures. The skeleton structure in which a quaternary carbon atom constituting a cyclic structure is bonded to two other cyclic structures may be, for example, a fluorene skeleton, a bisphenol fluorene skeleton, a bisaminophenyl fluorene skeleton, a fluorene skeleton having an epoxy group, or a fluorene skeleton having an acrylic group. The cardo structure may be, for example, a fluorene ring bound to a benzene ring.

The cardo resin can be synthesized by polymerizing a monomer having the cardo structure by reacting functional groups thereof with each other. The method for polymerizing monomers having the cardo structure may be, for example, ring-opening polymerization or addition polymerization. Examples of the monomers having the cardo structure include: cardo structure-containing bisphenol compounds, such as a bis(glycidyloxyphenyl)fluorene epoxy resin, a 9,9-bis(4-hydroxyphenyl)fluorene, and 9,9-bis(4-hydroxy-3-methylphenyl)fluorene; 9,9-bis(cyanoalkyl)fluorene compounds, such as 9,9-bis(cyanomethyl)fluorene; 9,9-bis(aminoalkyl)fluorene compounds, such as 9,9-bis(3-aminopropyl)fluorene; and combinations of two or more thereof. The cardo resin may be a copolymer of a monomer having the cardo structure and an additional monomer that can be copolymerized therewith.

The weight average molecular weight (Mw) of the cardo resin is preferably 1,000 to 100,000 and more preferably 1,000 to 50,000. Provided the weight average molecular weight is at least 1,000, the film formability can be improved, and provided the weight average molecular weight is 100,000 or less, the alkali developability is good.

The binder resin (A) may include one type of resin individually or a combination of two or more resins.

The amount of binder resin (A) contained in the photosensitive resin composition with respect to 100 parts by mass of the total of the binder resin (A), the low molecular weight organic compound (B), the radiation sensitive compound (C), and the colorant (D) may be 5 to 60 parts by mass, preferably 10 to 55 parts by mass, more preferably 10 to 50 parts by mass. Provided the amount of the binder resin (A) contained is at least 5 part by mass with respect to 100 parts by mass of the total, the residual film ratio, heat resistance and sensitivity are suitable. Provided the amount of the binder (A) contained is 60 parts by mass or less with respect to 100 parts by mass of the total, the optical density (OD value) of the film after baking may be 0.5 or more per μm of film thickness, and light shielding properties can be retained even after baking.

The binder resin (A) preferably includes at least one selected from the group consisting of resin components (a) to (k) and any combinations of a plurality of the resin components (a) to (k) are possible. The binder resin (A) more preferably includes at least one selected from the group consisting of resin components (a) to (d), even more preferably includes at least two selected from the group consisting of resin components (a), (c) and (d), and even more preferably still includes resin components (c) and (d). In another preferred embodiment, the binder resin (A) includes at least one selected from the group consisting of (a), (b), and (c).

With respect to 100 parts by mass of the binder resin (A), it is preferable for the amount of the at least one resin component selected from the group consisting of (a) to (d) to be 0.5 parts by mass or more, more preferably 50 parts by mass or more, and even more preferably 88 parts by mass or more. Provided the amount of the at least one resin component selected from the group consisting of (a) to (d) is at least 0.5 parts by mass with respect to 100 parts by mass of the binder resin (A), heat resistance of the resin composition is good.

The four types of resin component (a) to (d) may be used in combination. When using the four types in combination, it is preferable that in the binder resin (A), the proportion of the polyalkenylphenolic resin (a) be 5 to 50% by mass, the proportion of the hydroxypolystyrene resin derivative (b) be 5 to 30% by mass, the proportion of the aqueous alkaline solution-soluble resin having an epoxy group and a phenolic hydroxyl group (c) be 10 to 80% by mass, and the aqueous alkaline solution-soluble copolymer of a polymerizable monomer having an alkali-soluble functional group and an additional polymerizable monomer (d) be 10 to 80% by mass.

(B) Low Molecular Weight Organic Compound

The low molecular weight organic compound (B) has a molar volume of 130 cm³/mol or less at 20° C. and 1 atm and is selected from the group consisting of aromatic carboxylic acids and compounds each having a plurality of phenolic hydroxyl groups. Herein, “low molecular weight compound” refers to a compound with a molecular weight of 1,000 or less. Just a single type may be used for the low molecular weight organic compound (B) or a combination of two or more may be used.

Herein, aromatic hydroxy carboxylic acids each having a plurality of phenolic hydroxyl groups will be treated as aromatic carboxylic acids. In other words, the compounds each having a plurality of phenolic hydroxyl groups do not encompass those having a carboxyl group.

The low molecular weight organic compound (B) has a carboxyl group or a plurality of phenolic hydroxyl groups and is alkali-soluble. In addition thereto, the low molecular weight organic compound (B) is quickly eluted into the alkali developer from the coating formed using the photosensitive resin composition due to the small molar volume being 130 cm³/mol or less. The elution of the low molecular weight organic compound (B) from the coating results in the entanglement between polymer chains of the binder resin (A) being released, promoting the dissolution of the alkali-soluble parts of the binder resin (A) during development. In this way, the low molecular weight organic compound (B) can impart excellent alkali developability and pattern formability to the photosensitive resin composition even with low energy light exposure. Furthermore, as the low molecular weight organic compound (B) has a small molar volume of 130 cm³/mol or less, the compatibility or dispersibility thereof with the binder resin (A) and other components is excellent and thus uniform dissolution or dispersion thereof can be achieved in the photosensitive resin composition and the coating formed using the same. This advantageously enhances the smoothness and uniformity of the coating surface and also reduces outgassing caused by the low molecular weight organic compound (B).

As the low molecular weight organic compound (B) is an aromatic compound, the compound is not readily degenerated or decomposed during exposure to light or heat treatment. Accordingly, a high-quality coating can be formed and outgassing resulting from decomposition products of the low molecular weight organic compound (B) can be reduced. There are cases where the carboxyl group or the plurality of phenolic hydroxyl groups of the low molecular weight organic compound (B) contribute to the improvement in adhesion of the coating to the substrate.

The molar volume of the low molecular weight organic compound (B) at 20° C. and 1 atm may be 130 cm³/mol, preferably 75 to 120 cm³/mol, more preferably 80 to 110 cm³/mol, and even more preferably 85 to 100 cm³/mol.

In one embodiment, the low molecular weight organic compound (B) is an aromatic carboxylic acid having a pKa (acid dissociation constant) of 2.5 to 4.5 at 25° C. The pKa of the aromatic carboxylic acid is preferably 2.7 to 4.2 and more preferably 2.8 to 4.0. An aromatic carboxylic acid having a pKa in the aforementioned ranges can effectively promote the dissolution of the binder resin (A) and can impart excellent alkali developability and pattern formability to the photosensitive resin composition even with low energy light exposure. An aromatic carboxylic acid having a pKa of 2.5 or more has dissolving properties at a level where the dissolution suppressing effects brought about by an acid generator, such as a diazonaphthoquinone compound, on unexposed parts of the binder resin (A) are not lost, and even in a positive tone photosensitive resin composition, excellent pattern formation can be achieved without excessive dissolution of unexposed parts of the coating during development so as to maintain a sufficient level of thickness of the unexposed parts of the coating.

In one embodiment, the low molecular weight organic compound (B) is a compound having a plurality of phenolic hydroxyl groups and a pKa of 7.5 to 10 at 25° C. The compound having a plurality of phenolic hydroxyl groups preferably has a pKa of 7.8 to 9.8, and more preferably 8.0 to 9.6. A compound having a plurality of phenolic hydroxyl groups and a pKa in the aforementioned ranges can effectively promote the dissolution of the binder resin (A) and can impart excellent alkali developability and pattern formability to the photosensitive resin composition even with low energy light exposure. The pKa of compounds having a plurality of phenolic hydroxyl groups is sufficiently high so that the dissolution suppressing effects brought about by a photoacid generator, such as a diazonaphthoquinone compound, on unexposed parts of the binder resin (A) are not lost, and thus even in a positive tone photosensitive resin composition, excellent pattern formation can be achieved.

The low molecular weight organic compound (B) is preferably a compound in which a group other than carboxyl groups and phenolic hydroxyl groups is not bound to the carbon atoms constituting the aromatic ring. Such compounds have a high ratio of the number of carboxyl groups and phenolic hydroxyl groups to the molar volume, which further increases the solubility of the low molecular weight organic compound (B) in the developer and can more effectively promote the dissolution of the binder resin (A).

The aromatic carboxylic acid may be, for example: a polycarboxylic acid selected from the group consisting of phthalic acid (molar volume 114.4 cm³/mol, pKa 2.95), isophthalic acid (molar volume 114.4 cm³/mol, pKa 3.53), terephthalic acid (molar volume 114.4 cm³/mol, pKa 3.49), hemimellitic acid (molar volume 127 cm³/mol, pKa 2.8), trimellitic acid (molar volume 127.0 cm³/mol, pKa 2.84), and trimesic acid (molar volume 127.0 cm³/mol, pKa 2.98); or an aromatic hydroxycarboxylic acid selected from the group consisting of 2,3-dihydroxybenzoic acid (molar volume 98.8 cm³/mol, pKa 2.96), 2,4-dihydroxybenzoic acid (molar volume 98.8 cm³/mol, pKa 3.32), 2,5-dihydroxybenzoic acid (molar volume 98.8 cm³/mol, pKa 3.01), 3,5-dihydroxybenzoic acid (molar volume 98.8 cm³/mol, pKa 3.96), 2,3,4-trihydroxybenzoic acid (molar volume 97.2 cm³/mol, pKa 3.3), and gallic acid (molar volume 97.2 cm³/mol, pKa 4.33). From the standpoint of ease of adjusting the solubility in a developer, the aromatic carboxylic acid is preferably 2,4-dihydroxybenzoic acid, 2,3,4-trihydroxybenzoic acid, or trimellitic acid. From the standpoint of good pattern adhesion after development, the aromatic carboxylic acid is more preferably 2,4-dihydroxybenzoic acid or 2,3,4-trihydroxybenzoic acid.

The compound having a plurality of phenolic hydroxyl groups may be, for example, an aromatic polyol selected from the group consisting of catechol (molar volume 86.2 cm³/mol, pKa 9.50), resorcinol (molar volume 86.2 cm³/mol, pKa 9.45), hydroquinone (molar volume 86.2 cm³/mol, pKa 9.58), 1,2,4-benzenetriol (molar volume 84.7 cm³/mol, pKa 9.58), pyrogallol (molar volume 84.7 cm³/mol, pKa 9.28) and phloroglucinol (molar volume 84.7 cm³/mol, pKa 9.06). From the standpoint of ease of adjusting solubility in the developer, the compound having a plurality of phenolic hydroxyl groups is preferably 1,2,4-benzenetriol or phloroglucinol. From the standpoint of good pattern adhesion after development, the compound having a plurality of phenolic hydroxyl groups is more preferably phloroglucinol.

The molar volume and the pKa of the low molecular weight organic compound (B) can be found using a database, such as SciFinder® provided by CAS (Chemical Abstract Service).

The amount of the low molecular weight organic compound (B) contained in the photosensitive resin composition with respect to 100 parts by mass of the total of the binder resin (A), the low molecular weight organic compound (B), the radiation sensitive compound (C), and the colorant (D) may be 0.1 to 20 parts by mass, preferably 1 to 15 parts by mass, and more preferably 3 to 12 parts by mass. Provided the content of the low molecular weight organic molecule (B) is 0.1 parts by mass or more with respect to 100 parts by mass of the total, the solubility of the binder resin (A) can be effectively promoted, and provided the content is 20 parts by mass or less, excessive dissolution of the binder resin (A) can be suppressed and pattern formability, surface quality, etc., of the coating can be improved.

(C) Radiation Sensitive Compound

For the radiation sensitive compound, a photoacid generator, a photobase generator or a photopolymerization initiator may be used. The photoacid generator includes compounds that generate acid when exposed to radiation. As the photoacid generator increases the solubility in an aqueous alkaline solution of parts exposed to radiation, the photoacid generator can be used in positive tone photosensitive resin compositions in which the parts are made to be dissolved. The photobase generator includes compounds that generate a base when exposed to radiation. As the photobase generator decreases the solubility in an aqueous alkaline solution of parts exposed to radiation, the photobase generator can be used in negative tone photosensitive resin compositions in which the parts are made to be non-soluble. The photopolymerization initiator includes compounds that generate radicals when exposed to radiation. When the photosensitive resin composition comprises a radical polymerizable functional group-containing binder or a radical polymerizable compound, radical polymerization of irradiated parts of the radical polymerizable functional groups of the binder resin or the radical polymerizable compound proceeds, and a cured product which is insoluble in an aqueous alkaline solution is formed in the parts. Thus, the photopolymerization initiator can be used in negative tone photosensitive resin compositions.

It is preferable from the standpoint of achieving high sensitivity and high pattern resolution that the radiation sensitive compound (C) be a photoacid generator. For the photoacid generator, at least one selected from the group consisting of quinone diazide compounds, sulfonium salts, phosphonium salts, diazonium salts, and iodonium salts may be used. In one embodiment, the photoacid generator is a compound or salt with high sensitivity to i-rays (365 nm).

The use of a quinone diazide compound for the photoacid generator is preferable. The quinone diazide compound may be a polyhydroxy compound to which the sulfonic acid of the quinone diazide is bonded through an ester, a polyamino compound to which the sulfonic acid of the quinone diazide is bonded through a sulfonamide bond, a polyhydroxy polyamino compound to which the sulfonic acid of the quinone diazide is bonded through an ester or sulfonamide bond, etc. From the standpoint of contrast between exposed and unexposed parts, it is preferable that at least 20 mol % of the total of the functional groups of the polyhydroxy compound or polyamino compound be substituted with quinone diazide.

Examples of the polyhydroxy compound include, but not limited to, Bis-Z, BisP-EZ, TekP-4HBPA, TrisP-HAP, TrisP-PA, TrisP-SA, TrisOCR-PA, BisOCHP-Z, BisP-MZ, BisP-PZ, BisP-IPZ, BisOCP-IPZ, BisP-CP, BisRS-2P, BisRS-3P, BisP-OCHP, Methylenetris-FR-CR, BisRS-26X, DML-MBPC, DML-MBOC, DML-OCHP, DML-PCHP, DML-PC, DML-PTBP, DML-34X, DML-EP, DML-POP, dimethylol-BisOC-P, DML-PFP, DML-PSBP, DML-MTrisPC, TriML-P, TriML-35XL, TML-BP, TML-HQ, TML-pp-BPF, TML-BPA, TMOM-BP, HML-TPPHBA, HML-TPHAP (trade names, Honshu Chemical Industry Co., Ltd.), BIR-OC, BIP-PC, BIR-PC, BIR-PTBP, BIR-PCHP, BIP-BIOC-F, 4PC, BIR-BIPC-F, TEP-BIP-A, 46DMOC, 46DMOEP, TM-BIP-A (trade names, Asahi Yukizai Corporation), 2,6-dimethoxymethyl-4-t-butylphenol, 2,6-dimethoxymethyl-p-cresol, 2,6-diacetoxymethyl-p-cresol, naphthol, tetrahydroxybenzophenone, gallic acid methyl ester, bisphenol A, bisphenol E, methylene bisphenol, and BisP-AP (trade name, Honshu Chemical Industry Co., Ltd.).

Examples of the polyamino compound include, but not limited to, 1,4-phenylenediamine, 1,3-phenylenediamine, 4,4′-diaminodiphenyl ether, 4,4′-diaminodiphenylmethane, 4,4′-diaminodiphenyl sulfone, and 4,4′-diaminodiphenyl sulfide.

Examples of the polyhydroxypolyamino compound include, but not limited to, 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane, and 3,3′-dihydroxybenzidine.

Specific examples of the quinone diazide compound include a 1,2-naphthoquinonediazide-4-sulfonic acid ester and a 1,2-naphthoquinonediazide-5-sulfonic acid ester of a polyhydroxy compound.

The quinone diazide compound forms carboxyl groups when exposed to UV light, etc., through the reaction illustrated in reaction formula 2 below. The formation of the carboxyl group results in parts (coating) exposed to light becoming soluble in an aqueous alkaline solution and these parts exhibit alkali developability.

When the radiation sensitive compound (C) is a photoacid generator, the amount of the radiation sensitive compound (C) contained in the photosensitive resin composition may be, with respect to 100 parts by mass of the total of the binder resin (A), the low molecular weight organic compound (B), the radiation sensitive compound (C) and the colorant (D), 5 to 50 parts by mass, preferably 10 to 45 parts by mass, and more preferably 15 to 40 parts by mass. Provided the content of the radiation sensitive compound (C) with respect to 100 parts by mass of the total is at least 5 parts by mass, the alkali developability is good, and provided the content is 50 parts by mass or less, the reduction of coating due to heat treatment at 300° C. or more can be suppressed.

For the radiation sensitive compound (C), a photobase generator may be used. For the photobase generator, at least one selected from the group consisting of amide compounds and ammonium salts may be used. In one embodiment, the photobase generator is a compound or salt with high sensitivity to i-rays (365 nm).

Examples of the amide compound include 2-nitrophenylmethyl-4-methacryloyloxypiperidine-1-carboxylate, 9-anthrylmethyl-N,N-dimethyl carbamate, 1-(anthraquinone-2-yl)ethylimidazole carboxylate, (E)-1-[3-(2-hydroxyphenyl)-2-propenoyl]piperidine. The ammonium salt may be, for example, 1,2-diisopropyl-3-{bis(dimethylamino)methylene}guanidinium 2-(3-benzoylphenyl)propionate, (Z)-{[bis(dimethylamino)methylidene]amino}-N-cyclohexylamino)methanaminium tetrakis(3-fluorophenyl)borate, and 1,2-dicyclohexyl-4 4,5,5-tetramethylbiguanidinium n-butyltriphenylborate.

When the radiation sensitive compound (C) is a photobase generator, the amount of the radiation sensitive compound (C) contained in the photosensitive resin composition may be, with respect to 100 parts by mass of the total of the binder resin (A), the low molecular weight organic compound (B), the radiation sensitive compound (C) and the colorant (D), 0.1 to 25 parts by mass, preferably 0.5 to 20 parts by mass, and more preferably 1 to 15 parts by mass. Provided the content of the radiation sensitive compound (C) with respect to 100 parts by mass of the total is at least 0.1 parts by mass, the alkali developability is good, and provided the content is 20 parts by mass or less, the reduction of coating due to heat treatment at 300° C. or more can be suppressed.

For the radiation sensitive compound (C), a photopolymerization initiator may be used. For the photopolymerization initiator, at least one selected from the group consisting of benzyl ketal compounds, α-hydroxy ketone compounds, α-amino ketone compounds, acyl phosphine oxide compounds, oxime ester compounds, acridine compounds, benzophenone compounds, acetophenone compounds, aromatic keto ester compounds and benzoic acid esters compounds can be used. In one embodiment, the photopolymerization initiator is a compound with high sensitivity to i-rays (365 nm). As the sensitivity is high during light exposure, the photopolymerization initiator is preferably an α-hydroxy ketone compound, an α-amino ketone compound, an acyl phosphine oxide compound, an oxime ester compound, an acridine compound or a benzophenone compound, and more preferably an α-amino ketone compound, an acyl phosphine oxide compound, or an oxime ester compound.

The benzyl ketal compound may be, for example, 2,2-dimethoxy-1,2-diphenylethane-1-one. The α-hydroxy ketone compound may be, for example, 1-(4-isopropylphenyl)-2-hydroxy-2-methylpropan-1-one, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexyl phenyl ketone, 1-{4-(2-hydroxyethoxy)phenyl}-2-hydroxy-2-methylpropan-1-one, or 2-hydroxy-1-[4-{4-(2-hydroxy-2-methylpropionyl)benzyl]phenyl}-2-methylpropan-1-one. The α-aminoketone compound may be, for example, 2-dimethylamino-2-methyl-1-phenylpropan-1-one, 2-diethylamino-2-methyl-1-phenylpropan-1-one, 2-methyl-2-morpholino-1-phenylpropane-1-one, 2-dimethylamino-2-methyl-1-(4-methylphenyl)propan-1-one, 2-dimethylamino-1-(4-ethylphenyl)-2-methylpropan-1-one, 2-dimethylamino-1-(4-isopropylphenyl)-2-methylpropan-1-one, 1-(4-butylphenyl)-2-dimethylamino-2-methylpropan-1-one, 2-dimethylamino-1-(4-methoxyphenyl)-2-methylpropan-1-one, 2-dimethylamino-2-methyl-1-(4-methylthiophenyl)propan-1-one, 2-methyl-1-(4-methylthiophenyl)-2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butan-1-one, 2-benzyl-2-dimethylamino-1-(4-dimethylaminophenyl)-butan-1-one, 2-dimethylamino-2-[(4-methylphenyl)methyl]-1-[4-(4-morpholinyl))phenyl]-1-butanone. The acyl phosphine oxide compound may be, for example, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide or bis(2,6-dimethoxybenzoyl)-(2,4,4-trimethylpentyl)phosphine oxide. The oxime ester compound may be, for example, 1-phenylpropane-1,2-dione-2-(O-ethoxycarbonyl)oxime, 1-phenylbutane-1,2-dione-2-(O-methoxycarbonyl)oxime, 1,3-diphenylpropane-1,2,3-trione-2-(O-ethoxycarbonyl)oxime, 1-[4-(phenylthio)phenyl]octane-1,2-dione-2-(O-benzoyl)oxime, 1-[4-[4-(carboxyphenyl)thio]phenyl]propane-1,2-dione-2-(O-acetyl)oxime, 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl]ethanone-1-(O-acetyl)oxime, 1-[9-ethyl-6-[2-methyl-4-[1-(2, 2-dimethyl-1,3-dioxolan-4-yl)methyloxy]benzoyl]-9H-carbazol-3-yl]ethanone-1-(O-acetyl) oxime. The acridine compound may be, for example, 1,7-bis(acridin-9-yl)-n-heptane. The benzophenone compound may be, for example, benzophenone, 4,4′-bis(dimethylamino)benzophenone, 4,4′-bis(diethylamino)benzophenone, 4-phenylbenzophenone, 4,4-dichlorobenzophenone, 4-hydroxybenzophenone, alkylated benzophenones, 3,3′,4,4′-tetrakis(t-butylperoxycarbonyl)benzophenone, 4-methylbenzophenone, dibenzyl ketone or fluorenone. The acetophenone compound may be, for example, 2,2-diethoxyacetophenone, 2,3-diethoxyacetophenone, 4-t-butyldichloroacetophenone, benzalacetophenone or 4-azidobenzalacetophenone. The aromatic keto ester compound may be, for example, methyl 2-phenyl-2-oxyacetate. The benzoic acid ester compound may be, for example, ethyl 4-dimethylaminobenzoate, (2-ethyl)hexyl 4-dimethylaminobenzoate, ethyl 4-diethylaminobenzoate or methyl 2-benzoylbenzoate.

When the radiation sensitive compound (C) is a photopolymerization initiator, the amount of the radiation sensitive compound (C) contained in the photosensitive resin composition with respect to 100 parts by mass of the total of the binder resin (A), the low molecular weight organic compound (B), the radiation sensitive compound (C), and the colorant (D) can be 0.1 to 25 parts by mass, preferably 0.5 to 20 parts by mass, more preferably 1 to 15 parts by mass. Provided the content of the radiation sensitive compound (C) is at least 0.1 parts by mass with respect to 100 parts by mass of the total, the alkali developability is good, and provided the content is 20 parts by mass or less, the reduction of coating due to heating at 300° C. or more can be suppressed.

When the radiation sensitive compound (C) is a photopolymerization initiator, the photosensitive resin composition can further contain a radical polymerizable compound. Resins and compounds having a plurality of ethylenically unsaturated groups as the radical polymerizable compound can form crosslinking of coatings to increase the hardness thereof.

From the standpoint of reactivity during light exposure, and hardness, heat resistivity, etc., of the coating, the radical polymerizable compound is preferably a compound having a plurality of (meth)acrylic groups. Examples of the compound include diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, trimethylolpropane di(meth)acrylate, trimethylolpropane tri(meth)acrylate, ethoxylated trimethylolpropane di(meth)acrylate, ethoxylated trimethylolpropane tri(meth)acrylate, ditrimethylolpropane tri(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, 1,3-butanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, 1,10-decanediol di(meth)acrylate, dimethylol-tricyclodecane di(meth)acrylate, ethoxylated glycerin tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, ethoxylated pentaerythritol tri(meth)acrylate, ethoxylated pentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, tripentaerythritol hepta(meth)acrylate, tripentaerythritol octa(meth)acrylate, tetrapentaerythritol nona(meth)acrylate, tetrapentaerythritol deca(meth)acrylate, pentapentaerythritol undeca(meth)acrylate, pentapentaerythritol dodeca(meth)acrylate, ethoxylated bisphenol A di(meth)acrylate, 2,2-bis[4-(3-(meth)acryloxy-2-hydroxypropoxy)phenyl]propane, 1,3,5-tris((meth)acryloxyethyl)isocyanuric acid, 1,3-bis((meth)acryloxyethyl)isocyanuric acid, 9,9-bis[4-(2-(meth)acryloxyethoxy)phenyl]fluorene, 9,9-bis[4-(3-(meth)acryloxypropoxy)phenyl]fluorene and 9,9-bis(4-(meth)acryloxyphenyl)fluorene, and acid modified products, ethylene oxide modified products, and propylene oxide modified products thereof.

The amount of the radical polymerizable compound contained in the photosensitive resin composition with respect to 100 parts by mass of the binder resin (A) may be 15 to 65 parts by mass, and is preferably 20 to 60 parts by mass, and more preferably 25 to 50 parts by mass. Provided the content of the radical polymerizable compound is within the aforementioned ranges, the alkali developability is good and the heat resistivity of the cured coating can be improved.

(D) Colorant

The colorant (D) is selected from the group consisting of black dyes and black pigments. By forming black barrier ribs in organic EL elements using a photosensitive resin composition containing the colorant (D), the visibility of a display device, such as an organic EL display, etc., can be improved.

In one embodiment, the colorant (D) contains a black dye. For the black dye, a dye defined by the color index (C.I.) as solvent black 27 to 47 may be used. The black dye is preferably one defined by the C.I. as solvent black 27, 29 or 34. When at least one black dye of the dyes defined by the C.I. as solvent black 27 to 47 is used, the light shielding properties of the coating of the photosensitive resin composition after baking can be maintained. The black dye-containing photosensitive resin composition, compared to a black pigment-containing photosensitive resin composition, leaves less colorant residue during development and can form high definition patterns in the coating.

The amount of the colorant (D) contained in the photosensitive resin composition when the colorant (D) is a black dye with respect to 100 parts by mass of the total of the binder resin (A), the low molecular weight organic compound (B), the radiation sensitive compound (C), and the colorant (D) is preferably 1 to 70 parts by mass, more preferably 5 to 60 parts by mass, and even more preferably 10 to 50 parts by mass. Provided the content of the colorant (D) is at least 1 part by mass with respect to 100 parts by mass of the total, the light shielding properties of the coating after baking can be maintained, and provided the content of the colorant (D) is 70 parts by mass or less with respect to 100 parts by mass of the total, the residual film ratio, heat resistance, sensitivity, etc., are suitable.

A black pigment may be used for the colorant (D). The black pigment may be carbon black, carbon nanotubes, acetylene black, graphite, iron black, aniline black, titanium black, a perylene pigment, a lactam pigment, etc. These black pigments may be used after surface treatment has been carried out thereon. Examples of commercially available perylene pigments include K0084, K0086, pigment black 21, 30, 31, 32, 33 and 34 manufactured by BASF. An example of a commercially available lactam pigment includes Irgaphor® Black S 0100 CF manufactured by BASF. Due to having high light shielding properties, at least one selected from the group consisting of carbon black, titanium black, a perylene pigment, and a lactam pigment is preferable. For a negative tone photosensitive resin composition in which the radiation sensitive compound (C) is a photopolymerization initiator, it is advantageous for the colorant (D) to be a black pigment that is less likely to inhibit polymerization.

The amount of the colorant (D) contained in the photosensitive resin composition when the colorant (D) is a black pigment with respect to 100 parts by mass of the total of the binder resin (A), the low molecular weight organic compound (B), the radiation sensitive compound (C), and the colorant (D) is preferably 1 to 70 parts by mass, more preferably 5 to 60 parts by mass, and even more preferably 10 to 50 parts by mass. Provided the content of the colorant (D) is at least 1 part by mass with respect to 100 parts by mass of the total, sufficient light shielding properties can be achieved, and provided the content of the colorant (D) is 70 parts by mass or less with respect to 100 parts by mass of the total, the residual film ratio, sensitivity, etc. are suitable.

(E) Optional Component

The photosensitive resin composition may include a thermosetting agent, a surfactant, a colorant other than (D), etc., as an optional component. The optional component (E) is defined as any component that does not correspond to any of (A) to (D).

A thermal radical generator may be used for the thermosetting agent. A preferable thermal radical generator may be an organic peroxide. Specific examples thereof include organic peroxides with a 10 hour half-life temperature of 100 to 170° C., such as dicumyl peroxide, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, tert-butylcumyl peroxide, di-tert-butyl peroxide, 1,1,3,3-tetramethylbutyl hydroperoxide, and cumene hydroperoxide.

The amount of the thermosetting agent contained with respect to 100 parts by mass of the total of the binder resin (A), the low molecular weight organic compound (B), the radiation sensitive compound (C), the colorant (D), and other solid content (excluding the thermosetting agent) is preferably 5 parts by mass or less, more preferably 4 parts by mass or less, and even more preferably 3 parts by mass or less.

The photosensitive resin composition may include a surfactant in order to, for example, improve coatability, smoothness of the coating, or developability of the coating. Examples of the surfactant include: polyoxyethylene alkyl ethers, such as polyoxyethylene lauryl ether, polyoxyethylene stearyl ether, and polyoxyethylene oleyl ether; polyoxyethylene aryl ethers, such as polyoxyethylene octyl phenyl ether and polyoxyethylene nonyl phenyl ether; nonionic surfactants, such as polyoxyethylene dialkyl esters, including polyoxyethylene dilaurate and polyoxyethylene distearate; fluorosurfactants, such as Megaface® F-251, Megaface F-281, Megaface F-430, Megaface F-444, Megaface R-40, Megaface F-553, Megaface F-554, Megaface F-555, Megaface F-556, Megaface F-557, Megaface F-558, Megaface F-559 (trade names, DIC Corporation), Surflon® S-242, Surflon S-243, Surflon S-386, Surflon S-420, and Surflon S-611 (trade names, ACG Seimi Chemical Co., Ltd.); and organosiloxane polymers KP 323, KP 326, and KP 341 (trade names, Shin-Etsu Chemical Co., Ltd.). These may be used individually or in a combination of two or more.

The content of the surfactant with respect to 100 parts by mass of the total of the binder resin (A), the low molecular weight organic compound (B), the radiation sensitive compound (C), and the colorant (D) and other solid content (excluding the surfactant) is preferably 2 parts by mass or less, more preferably 1 part by mass or less, and even more preferably 0.5 parts by mass or less.

The photosensitive resin composition may include a second colorant other than the black dye and black pigment. The second colorant may be a dye, an organic pigment, an inorganic pigment, etc., and may be used according to the purpose thereof. The second colorant may be used in an amount that does not impair the effect of the invention.

Examples of the dye include an azo dye, a benzoquinone dye, a naphthoquinone dye, an anthraquinone dye, a cyanine dye, a squarylium dye, a croconium dye, a merocyanine dye, a stilbene dye, a diphenylmethane dye, a triphenylmethane dye, a fluoran dye, a spiropyran dye, a phthalocyanine dye, an indigo dye, a fulgide dye, a nickel complex dye, and an azulene dye.

Examples of the pigment include C. I. pigment yellow 20, 24, 86, 93, 109, 110, 117, 125, 137, 138, 147, 148, 153, 154, and 166, C.I. pigment orange 36, 43, 51, 55, 59, and 61, C.I. pigment red 9, 97, 122, 123, 149, 168, 177, 180, 192, 215, 216, 217, 220, 223, 224, 226, 227, 228, and 240, C.I. pigment violet 19, 23, 29, 30, 37, 40, and 50, C.I. pigment blue 15, 15:1, 15:4, 22, 60, and 64, C.I. pigment green 7, and C.I. pigment brown 23, 25, and 26.

(F) Solvent

The photosensitive resin composition may be dissolved in a solvent and used as a solution (note that when a black pigment is included, the pigment is in suspension). For example, by mixing specific amounts of the low molecular weight organic compound (B), the radiation sensitive compound (C), the colorant (D), and an optional component (E), such as a thermosetting agent or a surfactant, as needed, with a solution obtained by dissolving the binder (A) in the solvent (F), the photosensitive resin composition may be prepared in solution. The photosensitive resin composition may be adjusted to have a viscosity suitable for the coating method used by changing the amount of solvent.

Examples of the solvent include: glycol ethers, such as ethylene glycol monomethyl ether, ethylene glycol dimethyl ether, ethylene glycol methyl ethyl ether, and ethylene glycol monoethyl ether; ethylene glycol alkyl ether acetates, such as methyl cellosolve acetate, and ethyl cellosolve acetate; diethylene glycol compounds, such as diethylene glycol monomethyl ether, diethylene glycol diethyl ether, diethylene glycol dimethyl ether, diethylene glycol ethyl methyl ether, diethylene glycol monoethyl ether, and diethylene glycol monobutyl ether; propylene glycol alkyl ether acetate compounds, such as propylene glycol methyl ether acetate and propylene glycol ethyl ether acetate; aromatic hydrocarbons, such as toluene and xylene; ketones, such as methyl ethyl ketone, methyl amyl ketone, cyclohexanone, 4-hydroxy-4-methyl-2-pentanone, and cyclohexanone; esters, such as ethyl 2-hydroxypropionate, methyl 2-hydroxy-2-methylpropionate, ethyl 2-hydroxy-2-methylpropionate, ethyl ethoxyacetate, ethyl hydroxyacetate, methyl 2-hydroxy-2-methylbutanoate, methyl 3-methoxypropionate, ethyl 3-methoxypropionate, methyl 3-ethoxypropionate, ethyl 3-ethoxypropionate, ethyl acetate, butyl acetate, methyl lactate, ethyl lactate, and α-butyrolactone; amide compounds, such as N-methyl-2-pyrrolidone, N,N-dimethylformamide, and N,N-dimethylacetamide. These solvents may be used individually or in combination of two or more thereof.

The photosensitive resin composition may be prepared by dissolving or dispersing the binder resin (A), the low molecular weight organic compound (B), the radiation sensitive compound (C), the colorant (D), and the optional component (E) as necessary in the solvent (F) followed by mixing. The solid content concentration in the photosensitive resin composition may be determined as appropriate according to the intended use therefor. For example, the solid content concentration in the photosensitive resin composition may be 1 to 60% by mass, 3 to 50% by mass, or 5 to 40% by mass.

A publicly known method may be used for the dispersion mixing method when using a pigment. For example, a ball mill, a sand mill, a bead mill, a paint shaker, a ball type mill, such as a rocking mill, a kneader, a paddle mixer, a planetary mixer, a bladed type, such as a Henschel mixer, and a roll type mill, such as 3-roll mixer, may be used as well as a mortar machine, colloid mill, ultrasonic waves, a homogenizer, rotation and revolution mixer, etc. From the standpoint of dispersion efficiency and a fine dispersion, a bead mill is preferable.

The prepared photosensitive resin composition is usually filtered before use. The filtering means may be, for example, a millipore filter with a pore size of 0.05 to 1.0 μm.

Photosensitive resin compositions prepared in such a way have excellent long term storage stability.

When the photosensitive resin composition is used in radiation lithography, the photosensitive resin composition is first dissolved or dispersed in a solvent to prepare the coating composition. Next, the coating composition is applied on a substrate surface, the solvent is removed by heating, etc., and a coating can be formed. There are no particular restrictions on the method of applying the coating composition on the substrate surface and, for example, a spray method, a roll coating method, a slit method, or a spin coating method may be used.

After applying the coating composition onto the substrate surface, the solvent is typically removed by heating (pre-baking) to form a coating. Although the heating conditions will differ according to the type of components and the content thereof, etc., usually the coating can be obtained by heat treatment at 70 to 130° C., for example, for 1 to 20 minutes on a hot plate or for 3 to 60 minutes in an oven.

Next, the prebaked coating is exposed to radiation (e.g. visible light, ultraviolet, far-ultraviolet, X-rays, microwaves, gamma ray, synchrotron radiation, etc.) through a photomask having a predetermined pattern (light exposure step). When a quinone diazide compound is used as the radiation sensitive compound, the radiation used is preferably ultraviolet to visible light having a wavelength of 250 to 450 nm. In one embodiment the radiation is i-rays.

After the light exposure step, the coating is brought into contact with a developer and developed, unnecessary parts are removed and a pattern is formed on the coating (developing step). The developer may be an aqueous solution of an alkali compound, for example: an inorganic alkali, such as sodium hydroxide, potassium hydroxide, sodium carbonate, sodium silicate, sodium metasilicate, or ammonia water; a primary amine, such as ethylamine and n-propylamine; a secondary amine, such as diethylamine and di-n-propylamine; a tertiary amine, such as triethylamine and methyl diethylamine; an alcohol amine, such as dimethylethanolamine and triethanolamine; a quaternary ammonium salt, such as tetramethylammonium hydroxide, tetraethyl ammonium hydroxide, and choline; and a cyclic amine, such as pyrrole, piperidine, 1,8-diazabicyclo[5.4.0]-7-undecene, or 1,5-diazabicyclo[4.3.0]-5-nonane. An aqueous solution in which a water-soluble organic solvent, such as methanol or ethanol, a surfactant, etc., are added in appropriate amounts to the alkaline solution may be used as the developer. The developing time is usually 30 to 180 seconds. The developing method may be any one of the puddle method, shower method, or dipping method. After development, a pattern can be formed on the coating by cleaning with running water for 30 to 90 seconds, removal of unnecessary parts, and air drying with compressed air or compressed nitrogen.

Thereafter, the coating with the pattern formed thereon is heat treated with a heating device, such as a hot plate or an oven at, for example, 100 to 350° C. for 20 to 200 minutes to thereby obtain a cured coating (post-baking, heat treating step). During the heat treatment, the temperature may be maintained at a fixed temperature, continuously increased, or increased in a stepwise manner.

The optical density (OD value) of the cured coating of the photosensitive resin composition is preferably 0.5 or more per μm thickness of film, more preferably 0.7 or more, and even more preferably 1.0 or more. Provided the OD value of the cured coating is at least 0.5 per μm thickness of film, sufficient light shielding properties can be obtained.

One embodiment is a method of producing an organic EL element barrier rib comprising: preparing a coating composition by dissolving or dispersing a photosensitive resin composition in a solvent; forming a coating by applying the coating composition on a substrate; drying the coating by removing the solvent contained in the coating; irradiating the dried coating with radiation through a photomask thereby exposing the coating; forming a pattern on the coating by developing the exposed coating by bringing the coating into contact with a developer; and forming the organic EL element barrier rib by heat treating the coating on which the pattern is formed at a temperature of 100 to 350° C.

One embodiment is an organic EL element barrier rib comprising a cured photosensitive resin composition.

One embodiment is an organic EL element comprising a cured photosensitive resin composition.

EXAMPLES

The invention will be specifically explained based on the following examples and comparative examples but is not limited thereby.

The weight average molecular weight and the number average molecular weight of the binder resin (A) were calculated using a calibration curve created using a standard polystyrene under the following measurement conditions.

Name of equipment: Shodex® GPC-101

Column: Shodex® LF-804

Mobile phase: tetrahydrofuran

Flow rate: 1.0 mL/min

Detector: Shodex® RI-71

Temperature: 40° C.

(1) Synthesis of Binder Resin (A)

[Production Example 1] Production of Aqueous Alkaline Solution-Soluble Resin Having an Epoxy Group and a Phenolic Hydroxyl Group (c1)

150 g of EPICLON® N-695 (cresol novolak epoxy resin, epoxy equivalent 210 manufactured by DIC Corporation) as a compound having at least two epoxy groups per molecule was added to a 300 mL 3-neck flask filled with 300 g of α-butyrolactone (Mitsubishi Chemical Corporation) as a solvent, and dissolved under a nitrogen gas atmosphere at 60° C. 70.4 g (0.65 equivalents to 1 equivalent of epoxy) of 3,5-dihydroxybenzoic acid (Fujifilm Wako Pure Chemical Corporation) used as the hydroxybenzoic acid compound and 0.661 g (2.52 mmol) of triphenylphosphine (Tokyo Chemical Industry Co., Ltd.) as a reaction catalyst were added thereto and reacted for 24 hours at 110° C. The reaction solution was returned to room temperature and diluted to 20% by mass of solid components with α-butyrolactone, the solution was filtered and 804.2 g was collected (resin solution c1). The obtained reaction product had a number average molecular weight of 3,000 and a weight average molecular weight of 8,100.

[Production Example 2] Production of Aqueous Alkaline Solution-Soluble Resin Having an Epoxy Group and a Phenolic Hydroxyl Group (c2)

37.6 g of EPICLON® N-770 (phenol novolak epoxy resin, epoxy equivalent 188 manufacture by DIC Corporation) as a compound having at least two epoxy groups per molecule was added to a 300 mL 3-neck flask filled with 75.2 g of γ-butyrolactone (Mitsubishi Chemical Corporation) as a solvent and dissolved under a nitrogen gas atmosphere at 60° C. 20.1 g (0.65 equivalents to 1 equivalent of epoxy) of 3,5-dihydroxybenzoic acid (Fujifilm Wako Pure Chemical Corporation) used as the hydroxybenzoic acid compound and 0.173 g (0.660 mmol) of triphenylphosphine (Tokyo Chemical Industry Co., Ltd.) as a reaction catalyst were added thereto and reacted for 21 hours at 110° C. The reaction solution was returned to room temperature and diluted to 20% by mass of solid components with α-butyrolactone. The solution was filtered and 197.7 g was collected (resin solution c2). The obtained reaction product had a number average molecular weight of 2,400 and a weight average molecular weight of 8,300.

[Production Example 3] Production of Aqueous Alkaline Solution-Soluble Copolymer of a Polymerizable Monomer Having an Alkali-Soluble Functional Group and an Additional Polymerizable Monomer (d)

28.0 g of 4-hydroxyphenyl methacrylate (“PQMA” manufactured by Showa Denko K.K.) and 7.89 g of N-cyclohexyl maleimide (Nippon Shokubai Co., Ltd.) were completely dissolved in 77.1 g of 1-methoxy-2-propyl acetate (Daicel Corporation), and 3.66 g of V-601 (Fujifilm Wako Pure Chemical Corporation) used as a polymerization initiator was completely dissolved in 14.6 g of 1-methoxy-2-propyl acetate (Daicel Corporation). The resulting two solutions were both simultaneously dripped for two hours into 61.2 g of 1-methoxy-2-propyl acetate (Daicel Corporation) heated to 85° C. under a nitrogen atmosphere in a 300 mL 3-neck flask, and then reacted for three hours at 85° C. The reaction solution that had cooled to room temperature was dripped into 815 g of toluene and a copolymer was precipitated. The precipitated copolymer was recovered by filtration, and vacuum dried for 4 hours at 90° C. 32.4 g of white powder was collected. This was dissolved in α-butyrolactone and a resin solution having a solid concentration of 20% by mass was obtained (resin solution dl). The obtained reaction product had a number average molecular weight of 6,100 and a weight average molecular weight of 11,800.

(2) Raw Material

(A) Binder Resin

Resin solutions c1, c2 and dl synthesized in Production Examples 1 to 3 were used as the binder resin (A).

(B) Low Molecular Weight Organic Compound

Compounds shown in Table 1 were used as the low molecular weight organic compound (B). The molar volumes (cm³/mol) and pKa are cited in Scifinder®.

TABLE 1 Molar volume Name of compound Structure [cm³/mol] pKa 1,2,4-Benzenetriol

 84.7 9.58 Pyrogallol

 84.7 9.28 Phloroglucinol

 84.7 9.06 2,3,4-Trihydroxybenzoic acid

 97.2 3.30 Gallic acid

 97.2 4.33 2,3-Dihydroxybenzoic acid

 98.8 2.96 2,4-Dihydroxybenzoic acid

 98.8 3.32 2,5-Dihydroxybenzoic acid

 98.8 3.01 3,5-Dihydroxybenzoic acid

 98.8 3.96 Hemimellitic acid

127.0 2.80 Pyromellitic acid

139.5 1.87 Leucoquinizarin

151.3 8.11 Propyl gallate

155.6 7.94 2,3,4,4′- Tetrahydroxybenzophenone

161.2 7.38 Phenolphthalein

229.7 9.23 Phenolphthalin

242.0 3.96 (C) Radiation Sensitive Compound

Quinone diazide compound TS150-A (1,2-naphthoquinonediazide-5-sulfonic acid ester of α,α,α′-tris(4-hydroxyphenyl)-1-ethyl-4-isopropylbenzene (Toyo Gosei Co., Ltd.)), which is a photoacid generator, was used as the radiation sensitive compound. The structure of TS-150A is shown below. The sulfonic acid esterification rate for TS-150A is approximately 50%.

(D) Colorant

For the colorant, black pigment Valifast® Black 3804 (a black pigment defined by the C.I. as solvent black 34 (Orient Chemical Industries Co., Ltd.)) was used.

(E) Optional Components

For the surfactant, Megaface® F-559 (a fluorosurfactant (DIC Corporation)) was used.

(F) Solvent

For the solvent, α-butyrolactone was used.

(3) Preparation and Evaluation of the Photosensitive Resin Composition

Examples 1 to 10 and Comparative Examples 1 to 6

22.5 parts by mass (4.5 parts by mass solid component) of resin solution dl was mixed with 21 parts by mass (4.2 parts by mass solid component) of resin c1 and dissolved. To the resulting solution, 5 parts by mass of each low molecular weight organic compound (B) listed in Table 1, 22 parts by mass of TS-150A, 29.5 parts by mass Valifast® Black 3804, and 0.14 parts by mass of Megaface® F-559, and a diluting solvent were added and further mixing was carried out. After visually confirming the mixture had dissolved, filtration using a 0.22 μm pore diameter millipore filter was carried out and a photosensitive resin composition having a solid content concentration of 12% by mass was prepared.

For each photosensitive resin composition prepared in the Examples and Comparative Examples, pattern formability, residue, surface state, and ITO adhesiveness were evaluated. The results are shown in Table 2. The evaluation methods are described below.

[Pattern Formability and Residue]

The photosensitive resin compositions of Examples 1 to 10 and Comparative Examples 1 to 6 were each applied onto an indium tin oxide (ITO) film of a glass substrate (70 mm×70 mm×0.7 mm) having thereon the ITO film by barcoating such that the dry film thickness was 1 to 2 μm, then the solvent was dried for 80 seconds at 120° C. Further, the resin composition was exposed to only i-rays of 100 mJ/cm² with an exposure apparatus (trade name Multilight ML-251A/B, manufactured by Ushio Inc.), in which an ultrahigh pressure mercury lamp was incorporated, through a bandpass filter for mercury lamp exposure (trade name HB0365 Asahi Spectra Co., Ltd.) and a quartz photomask. The line and space (L/S) pattern of the photomask was 10 μm. The amount of exposure was measured using an accumulated UV meter (trade name UIT-150, light receiving unit UVD-5365, manufactured by Ushio Inc.). Exposed coatings were alkali developed for 60 seconds with an aqueous solution of 2.38% by mass of tetramethylammonium hydroxide using a spin development device (AD-1200, manufactured by Takizawa Sangyo K.K.). Thereafter, the coating was cured for 60 minutes at 250° C. in a nitrogen atmosphere and a pattern sample was obtained. Observations were carried out using an optical microscope (VHX-6000, manufactured by Keyence Corporation). When there was no residue after alkali development, including in edge parts of the pattern, then the coating was judged to be “good”. When there was residue, then the coating was judged to be “defective”.

Coatings for which both pattern formability and residue were good were judged to be “good” with respect to pattern formability and residue and everything else was judged to be “defective”.

[State of Surface]

After forming such a pattern as described above, an optical microscope (VHX-6000, manufactured by Keyence Corporation) was used to determine whether the surface had an orange peel finish or whether there were variations in the color. Those that were determined not to have parts with an orange peel finish nor to have unevenness in color were judged to be “good” and those that were determined to have even one of the orange peel finish or the unevenness in color were judged to be “defective”.

[Adhesiveness to ITO]

After forming such a pattern as described above, an optical microscope (VHX-6000, manufactured by Keyence Corporation) was used to determine whether the pattern was formed in accordance with the photomask. Those in which a pattern remained in accordance with the photomask were judged to be “good”, and those in which a part of the pattern had peeled off were judged to be “defective”.

TABLE 2 Evaluation Results Low molecular weight organic compound (B) Pattern Molar formability volume¹⁾ and State of Adhesiveness Compound Name [cm³/mol] pKa¹⁾ Residue surface to ITO Example 1 1,2,4-benzenetriol 84.7 9.58 Good Good Good Example 2 pyrogallol 84.7 9.28 Good Good Good Example 3 phloroglucinol 84.7 9.06 Good Good Good Example 4 2,3,4-trihydroxybenzoic acid 97.2 3.30 Good Good Good Example 5 Gallic acid 97.2 4.33 Good Good Defective Example 6 2,3-dihydroxybenzoic acid 98.8 2.96 Good Good Good Example 7 2,4-dihidroxybenzoic acid 98.8 3.32 Good Good Good Example 8 2,5-dihydroxybenzoic acid 98.8 3.01 Good Good Good Example 9 3,5-dihydroxybenzoic acid 98.8 3.96 Good Good Good Example 10 hemimellitic acid 127.0 2.80 Good Good Good Comparative pyromellitic acid 139.5 1.87 Defective Good Good Example 1 Comparative leucoquinizarin 151.3 8.11 Defective Defective Good Example 2 Comparative propyl gallate 155.6 7.94 Defective Defective Good Example 3 Comparative 2,3,4,4′- 161.2 7.38 Defective Good Good Example 4 tetrahydroxybenzophenone Comparative phenolphthalein 229.7 9.23 Defective Defective Good Example 5 Comparative phenolphthalin 242.0 3.96 Defective Good Good Example 6 ¹⁾Cited in Scifinder ®

Examples 11 to 15

A photosensitive resin composition was prepared in the same way as for Example 1 using the component shown in Table 3. With respect to the photosensitive resin compositions prepared in each Example, the film thickness, the OD value after heating, the solubility of unexposed parts and the residual film ratio were evaluated. The results are illustrated in Table 3. The evaluation methods are described below.

[Film Thickness]

The 10 μm L/S portion of the pattern sample after pattern formation and residue had been observed was measured using a surface roughness meter (Surfcom 130A, manufactured by Tokyo Seimitsu Co., Ltd.).

[OD Value after Heating]

The photosensitive resin compositions of Examples 11 to 15 were spin coated onto a glass substrate (100 mm×100 mm×1 mm) so as to have a dry film thickness of approximately 1.5 μm then heated on a hotplate for 80 seconds at 120° C. to dry off the solvent. Then, the coating was obtained by curing for 60 minutes at 250° C. under a nitrogen atmosphere. The OD value of the cured coating was measured with a transmission densitometer (BMT-1, manufactured by Sakata Inx Eng. Co., Ltd.), corrected using the OD value of only glass, and converted to an OD value per μm thickness of the coating. The thickness of the coating was measured using an optical film thickness measuring device (F20-NIR, manufactured by Filmetrics Japan, Inc.).

[Solubility of Unexposed Parts]

The photosensitive resin compositions of Examples 11 to 15 were each barcoated onto a glass substrate (70 mm×70 mm×0.7 mm) on which an ITO film was attached so as to have a dry film thickness of 1.5 to 2.0 μm and then heated on a hotplate for 80 seconds at 120° C. to dry off the solvent. The dry film thickness was measured using an optical film thickness measuring device (F20-NIR, manufactured by Filmetrics Japan, Inc.), and then the coating was alkali developed for 60 seconds with an aqueous solution of 2.38% by mass of tetramethylammonium hydroxide using a spin development device (AD-1200, manufactured by Takizawa Sangyo K.K.). The film thickness after alkali development was again measured using the optical film thickness measuring device (F20-NIR, manufactured by Filmetrics Japan, Inc.) and the film thickness dissolved during development was calculated as the solubility of the unexposed part.

[Residual Film Ratio]

After measuring the solubility of the unexposed parts, the coating was cured for 60 minutes at 250° C. under a nitrogen atmosphere and the film thickness of the cured coating was measured using the optical film thickness measuring device (F20-NIR, manufactured by Filmetrics Japan, Inc.). The residual ratio was calculated for each measurement value according to the following formula. Residual ratio (%)=film thickness after dissolution of unexposed part (development) and curing/film thickness before dissolving unexposed part.

TABLE 3 (Numerical values in parentheses are solid contents) Example Example Example Example Example 11 12 13 14 15 Composition (A) Binder resin Resin solution d1 22.5 23.5 24.0 22.5 25.5 (parts by mass) (4.5) (4.7) (4.8) (4.5) (5.1) Resin solution c1 21.0 20.0 20.0 21.0 — (4.2) (4.0) (4.0) (4.2) Resin solution c2 — — — — 17.0 (3.4) (B) Low molecular 2,4-dihydroxibenzoic acid 5.0 5.0 5.0 — — weight organic 2,3,4-trihydroxibenzoic acid — — — 5.0 — compound Phloroglucinol — — — — 5.0 (C) Radiation sensitive TS-150A 22.0 22.0 22.0 22.0 22.0 compound (E) Colorant VALIFAST BLACK 3804 29.5 29.5 29.0 29.5 29.5 (F) Surfactant Megaface ® F-559 0.14 0.14 0.14 0.14 0.14 Evaluation results Film thickness (μm) 1.00 0.96 1.02 0.98 0.95 OD value after heating (/μm) — 1.03 to 1.03 to 1.02 to — 1.06 1.05 1.04 Solubility of unexposed part 0.60 0.41 0.60 0.63 0.32 (μm) Residual film ratio (%) 56 62 56 55 66

INDUSTRIAL APPLICABILITY

The photosensitive resin composition according to the present disclosure can be favorably used in radiation lithography for forming barrier ribs for organic EL elements. Organic EL elements provided with barrier ribs formed by using the photosensitive resin composition of the present disclosure can be favorably used for electrical components in a display device that shows good contrast. 

The invention claimed is:
 1. A photosensitive resin composition for a light shielding barrier rib of an organic EL element comprising: (A) a binder resin; (B) at least one low molecular weight organic compound having a molar volume of 130 cm³/mol or less and being selected from the group consisting of aromatic carboxylic acids and compounds each having a plurality of phenolic hydroxyl groups; (C) a radiation sensitive compound; and (D) a colorant selected from the group consisting of black dyes and black pigments, wherein the binder resin (A) comprises (c) an aqueous alkaline solution-soluble resin having an epoxy group and a phenolic hydroxyl group, and the amount of the colorant (D) contained in the photosensitive resin composition is 1 part by mass to 70 parts by mass with respect to 100 parts by mass of the total of the binder resin (A), the low molecular weight organic compound (B), the radiation sensitive compound (C), and the colorant (D).
 2. The photosensitive resin composition according to claim 1 wherein the low molecular weight organic compound (B) is an aromatic carboxylic acid having a pKa of 2.5 to 4.5.
 3. The photosensitive resin composition according to claim 1 wherein the low molecular weight organic compound (B) is a compound having a plurality of phenolic hydroxyl groups and having a pKa of 7.5 to
 10. 4. The photosensitive resin composition according to claim 1 wherein a group other than carboxyl groups and phenolic hydroxyl groups is not bound to the carbon atoms constituting the aromatic ring of the low molecular weight organic compound (B).
 5. The photosensitive resin composition according to claim 1 wherein the compound having a plurality of phenolic hydroxyl groups is an aromatic polyol selected from the group consisting of catechol, resorcinol, hydroquinone, 1,2,4-benzenetriol, pyrogallol and phloroglucinol.
 6. The photosensitive resin composition according to claim 1 wherein the aromatic carboxylic acid is a polycarboxylic acid selected from the group consisting of isophthalic acid, terephthalic acid, hemimellitic acid, trimellitic acid, and trimesic acid; or an aromatic hydroxycarboxylic acid selected from the group consisting of 2,3-dihydroxybenzoic acid, 2,4-dihydroxybenzoic acid, 2,5-dihydroxybenzoic acid, 3,5-dihydroxybenzoic acid, 2,3,4-trihydroxybenzoic acid, and gallic acid.
 7. The photosensitive resin composition according to claim 1 comprising 0.1 parts by mass to 20 parts by mass of the low molecular weight organic compound (B) with respect to 100 parts by mass of the total of the binder resin (A), the low molecular weight organic compound (B), the radiation sensitive compound (C), and the colorant (D).
 8. The photosensitive resin composition according to claim 1 wherein the radiation sensitive compound (C) is at least one photoacid generator selected from the group consisting of quinone diazide compounds, sulfonium salts, phosphonium salts, diazonium salts, and iodonium salts.
 9. The photosensitive resin composition according to claim 1 wherein the binder resin (A) has an alkali-soluble functional group.
 10. The photosensitive resin composition according to claim 1 comprising a photoacid generator as 5 parts by mass to 50 parts by mass of the radiation sensitive compound (C) with respect to 100 parts by mass of the total of the binder resin (A), the low molecular weight organic compound (B), the radiation sensitive compound (C), and the colorant (D).
 11. The photosensitive resin composition according to claim 1 wherein the optical density (OD value) of a cured coating of the photosensitive resin composition is at least 0.5 per μm of film thickness.
 12. The photosensitive resin composition according to claim 1 wherein the binder resin (A) further comprises at least one selected from the group consisting of: (a) a polyalkenylphenolic resin having a structural unit represented by formula (1)

wherein in formula (1), R¹, R², and R³ each independently represent a hydrogen atom; an alkyl group with 1 to 5 carbon atoms; an alkenyl group represented by formula (2)

wherein in formula (2), R⁶, R⁷, R⁸, R⁹, and R¹⁰ each independently represent a hydrogen atom, an alkyl group with 1 to 5 carbon atoms, a cycloalkyl group with 5 to 10 carbon atoms, or an aryl group with 6 to 12 carbon atoms, the * in formula (2) represents the bond with the carbon atom constituting the aromatic ring; an alkoxy group with 1 or 2 carbon atoms; or a hydroxyl group, and at least one of R¹, R² and R³ is the alkenyl group represented by formula (2), Q is an alkylene group represented by the formula —CR⁴R⁵—, a cycloalkylene group with 5 to 10 carbon atoms, a divalent organic group having an aromatic ring, a divalent organic group having an alicyclic fused ring, or a divalent group consisting of a combination thereof, R⁴ and R⁵ each independently represent a hydrogen atom, an alkyl group with 1 to 5 carbon atoms, an alkenyl group with 2 to 6 carbon atoms, a cycloalkyl group with 5 to 10 carbon atoms or an aryl group with 6 to 12 carbon atoms; (b) a hydroxypolystyrene resin derivative having a structural unit represented by formula (3)

wherein in formula (3), R¹¹ is a hydrogen atom or an alkyl group with 1 to 5 carbon atoms, a is an integer from 1 to 4, b is an integer from 1 to 4, a+b is within the range of 2 to 5, R¹² is at least one selected from the group consisting of a hydrogen atom, a methyl group, an ethyl group and a propyl group; and (d) an aqueous alkaline solution-soluble copolymer of a polymerizable monomer having an alkali-soluble functional group and an additional polymerizable monomer.
 13. An organic EL element barrier rib comprising a cured product of the photosensitive resin composition according to claim
 1. 14. An organic EL element comprising a cured product of the photosensitive resin composition according to claim
 1. 